Winemaking Lees
The art of taking grapes from the vine and turning them into wine has been practiced for hundreds of years. In the process, a number of products that are useful to the creation of the wine yet undesirable in the finished product are created. Among them, wine lees have to be carefully managed to enable them to do their job yet not ruin the final flavors and appeal of the wine. Does this Spark an idea?
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Composition
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Wine lees are most easily described as the sediments that settle out of the wine during the fermentation process. The major components of the wine lees are cells from dead yeast and pulp and other parts of the grape that are left over from the pressings. Lees will continue to build up throughout the fermentation process as the grape remnants settle out and more yeast cells naturally die as a result of the increased alcohol content.
Benefits
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The lees can actually have a positive impact on the wine-making process. The lees can add beneficial protein to the wine thanks to the death of the yeast cells. Their presence can provide fuller flavor, and they can even affect the fullness or body of the wine if they are left in during the fermentation process. Food chemists can break down the action of the lees and talk about the chemicals that go in and out of the wine very precisely, but the end result is usually more flavor and a refinement of flavors if the lees are handled correctly.
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Removal
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The wine lees need to be removed as the aging process progresses. This is for a number of reasons, the most obvious of which is that no one wants to drink sediments with their wine. Winemakers need to be exceedingly careful when drawing the wine off the lees, as they do not want to allow extra oxygen to creep into the wine and also need to avoid stirring the lees, which can take weeks and sometimes longer to settle.
The process of siphoning the wine from the lees is known as racking. The easiest method is to have the settled wine on a higher level than the container that will receive it via a simple siphoning system. The wine must gently flow into the new container without mixing in too much oxygen from the surrounding air. Inevitably, some wine at the bottom of the original cask is lost, but winemakers err on the side of caution, as siphoning the lees into the new cask would defeat the purpose of racking.
Problems
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While lees do provide a number of benefits to the wine as it ferments, mishandling of lees can cause the entire batch of wine to be ruined. As previously stated, a large component of wine lees is the dead yeast cells that are falling out of solution. The yeast produce alcohol but also die in the presence of too much alcohol. Therefore, as the fermentation process proceeds, progressively larger quantities of wine lees result. As the dead yeast cells decompose, they release hydrogen sulfide gas, which is the same gas released by decomposing eggs as they rot. If the lees are allowed to decompose for too long, the hydrogen sulfide will irreparably harm the flavor of the wine.
Solutions
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There is a fine line between allowing the lees to perform their job and leaving them too long. The simplest method of preventing the decomposition from causing problems is to stir the wine during fermentation. Doing this early on can allow you to keep the wine on the lees for a longer period of time before the first racking of the wine and thus allow the lees to affect the flavors positively. If you stir the lees, however, you will accelerate the loss of the desirable sulfur dioxide gas created by the addition of Campden tablets or similar product. In order to regain this protection, simply add more Campden to the second vessel used during the racking. Usually you can repeat this during every other racking.
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