Lees are the spent yeast cells and other fine particles left after fermentation. A wine may be separated from its lees quickly, or it may spend time in contact with them. That contact can change texture, aroma, stability, and complexity.
The phrase sur lie means "on the lees." It is most often associated with white wines and sparkling wines, but lees management can matter in many styles.
What lees can add
Lees contact can make a wine feel rounder, creamier, or fuller. It can contribute subtle savory, bready, nutty, doughy, or yeasty notes. In sparkling wines made by the traditional method, time on lees is one reason wines can develop aromas of bread, biscuit, brioche, toast, or pastry.
Lees contact can also influence how oxygen affects the wine. In some contexts, lees may help protect wine from oxidation or change how it develops during aging. The effect depends on the type of lees, contact time, vessel, temperature, stirring, and overall winemaking plan.
Gross lees and fine lees
Not all lees are equal. Gross lees are heavier deposits that may include more grape solids and larger particles. Fine lees are smaller, more refined particles that can be useful for aging. Many producers remove gross lees and age wine on fine lees.
Leaving wine too long on unsuitable lees can create unpleasant aromas or instability. Careful lees management is therefore important.
Stirring the lees
Lees stirring, often called bâtonnage, moves lees back into suspension. This can increase texture and richness, especially in barrel-fermented white wines. It is associated with some Chardonnay styles, but it is not limited to Chardonnay.
Too much stirring can make a wine feel heavy or blur freshness. Many modern producers use less bâtonnage than in past fashion cycles, especially when they want precision and tension.
Lees in sparkling wine
Traditional-method sparkling wines undergo a second fermentation in bottle and then age on lees before disgorgement. This is a defining part of the method. The length of lees aging can vary by region, legal category, and producer decision.
What this means in the glass
A wine with lees influence may feel creamier or more layered than a wine made only for bright primary fruit. Look for terms such as sur lie, lees aged, barrel fermented, or traditional method. But do not assume lees always means obvious yeast flavor. In many wines, the effect is more about texture than aroma.