What Are Lees in Wine? Sur Lie Aging Explained

If you have ever noticed the words “sur lie” on a wine label, particularly on bottles of Muscadet or Champagne, you have encountered one of the most important and transformative techniques in winemaking. Understanding lees and how they interact with wine reveals a fascinating dimension of how winemakers craft texture, flavor, and complexity.

What Are Lees?

Lees are the sediment that accumulates at the bottom of a wine vessel during and after fermentation. This sediment consists primarily of dead yeast cells that have completed their work of converting sugar into alcohol, along with grape fragments, precipitated proteins, and tartrate crystals. There are two types of lees: gross lees, the heavy sediment that settles immediately after fermentation, and fine lees, the lighter particles that remain suspended longer before settling.

Winemakers typically remove the gross lees quickly after fermentation, as they can impart off-flavors if left in contact with the wine. However, the fine lees are a different matter entirely. Extended contact with fine lees, known as sur lie aging, is a deliberate and valued technique that fundamentally changes the character of the finished wine.

Why Lees Matter

When wine sits on its fine lees, a process called autolysis occurs. The dead yeast cells gradually break down, releasing proteins, mannoproteins, amino acids, and other compounds into the wine. These substances have several important effects.

First, they add richness and body. Mannoproteins contribute a creamy, round mouthfeel that makes the wine feel fuller and more luxurious on the palate. This is one reason why sur lie aged wines are often described as creamy, rich, or textured, even when they are technically dry.

Second, lees contact adds flavor complexity. Depending on the duration and conditions of aging, lees can contribute biscuit, brioche, bread dough, toasted nut, and savory umami notes. These flavors are particularly prominent in Champagne, where extended lees aging is one of the defining characteristics of the traditional method.

Third, lees protect wine from oxidation. The dead yeast cells consume small amounts of dissolved oxygen in the wine, acting as a natural buffer against premature oxidation. This allows winemakers to use less sulfur dioxide, resulting in wines that can taste more natural and expressive.

Fourth, lees improve a wine’s ability to age. The proteins released during autolysis contribute to wine stability and help preserve freshness over time.

Lees in Practice

Champagne is the most famous application of extended lees aging. After the secondary fermentation that creates the bubbles occurs in the bottle, the wine sits on its lees for a minimum of 15 months for non-vintage Champagne and 36 months for vintage Champagne. Many premium producers far exceed these minimums, aging their wines on lees for five, ten, or even twenty years. This extended contact is what gives great Champagne its characteristic biscuity, toasty, brioche-like complexity, distinguishing it from simpler sparkling wines that spend less time on their lees.

Muscadet Sur Lie from the Loire Valley is another classic example. Muscadet is made from the Melon de Bourgogne grape, which can produce fairly neutral wine on its own. But when aged on its lees over winter until bottling the following spring, the wine gains a creamy texture, subtle yeasty complexity, and a slight spritz of carbon dioxide that adds freshness. The “Sur Lie” designation on the label guarantees that this lees aging has taken place.

White Burgundy producers frequently use lees contact to build complexity in their Chardonnays. The wine rests in barrel on its fine lees, and the winemaker may practice batonnage, the periodic stirring of the lees with a rod to increase the interaction between wine and sediment. This technique enhances the creamy texture and integrates the oak character more seamlessly.

Other regions and styles that employ sur lie aging include Cava from Spain, Franciacorta from Italy, some Chenin Blanc producers in the Loire Valley and South Africa, and certain white Rhone wines made from Marsanne and Roussanne.

The duration of lees contact matters significantly. A few months of sur lie aging adds subtle texture and roundness. Several years, as in premium Champagne, develops pronounced biscuit and brioche character. The winemaker’s decision about how long to leave the wine on its lees is one of the key choices that shapes the final wine’s personality.

Explore with Sommo

Understanding winemaking techniques like lees aging helps you appreciate why certain wines taste the way they do. With Sommo, you can explore how production methods influence flavor by scanning bottles and learning about the winemaking behind each one, from brief sur lie contact to decades of lees aging in Champagne cellars.