Lees in wine refers to the sediment or debris that settles at the bottom of the wine vat after fermentation and aging. It is primarily composed of dead yeast cells, but can also include other particles such as grape skins, pulp, and seeds. This sediment is a natural byproduct of the winemaking process and plays a significant role in shaping the characteristics of the wine.
During fermentation, yeast consumes the sugars in the grape juice and converts them into alcohol. As the yeast cells complete their life cycle, they die and settle to the bottom of the vat. This sediment, known as lees, can vary in appearance, ranging from fine particles to larger clumps, depending on the winemaking techniques employed.
One method to separate the wine from the lees is through a process called fining. Fining agents, such as bentonite clay or egg whites, are added to the wine to help clarify it by attracting and binding with the particles in the lees. The wine is then either racked off the sediment or filtered, leaving behind a clear and refined wine.
However, some winemakers choose to leave the wine in contact with the lees for an extended period, a technique known as sur lie aging. This process can contribute additional complexity and flavors to the wine. As the lees break down, they release compounds such as amino acids, proteins, and polysaccharides, which can enhance the mouthfeel and contribute to a richer, creamier texture. Sur lie aging is often used in the production of white wines, such as Chardonnay, to add depth and character.
In my experience as a sommelier, I have tasted wines that have undergone sur lie aging and have found them to possess a distinct creaminess and complexity compared to wines that have been separated from the lees early on. The extended contact with the lees imparts unique flavors and aromas, such as brioche, hazelnut, or even a subtle yeasty note, which can be quite enjoyable.
It is worth noting that not all wines benefit from sur lie aging. Some wines, particularly lighter and more delicate varieties, may not harmonize well with the lees-derived flavors and textures. The decision to utilize sur lie aging or separate the wine from the lees is ultimately a winemaker's choice, based on their desired style and the characteristics of the grapes.
To summarize, lees in wine are the sediments that settle at the bottom of the vat after fermentation and aging. They consist primarily of dead yeast cells but can also include other particles. The presence of lees can influence the wine's texture, mouthfeel, and flavor profile. Whether to separate the wine from the lees or age it sur lie is a winemaking decision that can greatly impact the final product.