Understanding the Role Of Lees in Winemaking

Lees play a crucial part in making wine, especially in sparkling wines and high-end whites. Lees are leftovers from making wine, made up of used yeast cells, grape skins that settles after fermentation. Their impact on the wine’s character is significant yet subject to ongoing debate and study.

Understanding Lees and Their Composition

There are two types of lees: primary or gross lees and fine lees. Primary or gross lees are formed during initial fermentation. Fine lees develop after the first fermentation.

Gross lees are rich in grape particulates, tannins, and tartaric acid, whereas fine lees are more nuanced. Over time, dead yeast cells in the lees change through a process called yeast autolysis. This process releases various compounds, including polysaccharides, glucans, mannoproteins, and chitin, which significantly influence the wine’s final characteristics.

The Role of Mannoproteins in Wine

Yeast cells release mannoproteins, which are important for a wine’s smell, texture, stability, and ability to age. These complex proteins, enriched with carbohydrates, particularly mannose sugars, interact with the aging wine to create the distinctive characteristics associated with lees aging.

Effect of Lees Aging on Sensory Perception

In the conventional method of sparkling wine productions (second fermentation), lees aging imparts a unique toasty, brioche-like aroma, essential to the character of wines, like vintage Champagne.

Usually sparkling wines are removed from the lees after 12 months. However, the brioche-aromas begin to develop after 15 months. This aroma comes from yeast autolysis, similar to the yeast used in bakeries or beer making.

Furthermore, lees aging enhances the texture of these wines. Compounds like yeast mannoproteins contribute to foam stability, resulting in silkier, creamier bubbles and an overall smoother mouthfeel.

Mannoproteins and lees can mix with barrel flavors, changing the taste of oaky nuances and astringency in wines. This interaction enhances the wine’s harmony and integration, particularly affecting the mid-palate.

Enhancing Stability and Reducing Oxidation

Beyond sensory attributes, lees aging plays a vital role in the wine’s stability. Wines aged sur lie are less likely to have crystal formation due to potassium bitartrate instability. Lees also offer protection against oxidation, particularly in white wines aged in casks, by absorbing oxygen.

Techniques to Maximize Lees' Benefits

Winemakers employ various techniques to enhance the effects of lees aging. Bâtonnage, the process of stirring lees, is a traditional method that increases the breakdown of glucans and the concentration of mannoproteins.

Alternatively, adding fresh lees or enzymatic supplements like glucanase can expedite the breakdown of yeast cell walls.

Considerations and Limitations

While the benefits of lees aging are generally positive, careful management is essential. Monitoring the health of lees is crucial, as grapes affected by conditions like botrytis or oidium can introduce undesirable aromas.

Additionally, the ability of lees to absorb oxygen and protect the wine tends to diminish after about 3.5 years. Moreover, in red wines, excessive lees contact can impact color stability because of the interaction of mannoproteins with anthocyanins.

Additional Uses of Lees

Interestingly, the use of lees extends beyond wine aging. In Burgundy, they sometimes make Fine de Bourgogne by distilling fine lees. This captures the taste and complexity that comes from aging.

The intricate interplay between lees and wine is a testament to the art and science of winemaking. Knowing and using the qualities of lees can greatly impact how a wine smells, feels, stays good, and its overall quality, highlighting the importance of lees in winemaking.

Thanks for Reading!

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This text was neither commissioned nor compensated. It reflects exclusively my own opinion.


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