Is "sitting on the lees" the same as "malolactic fermentation"?

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Dear Dr. Vinny,

I've heard that certain white wines are allowed to "sit on the lees" for added texture and complexity. Is this the same as malolactic fermentation?

—Jay E., Boston

Dear Jay,

No, these are two different winemaking processes that are independent from each other (though both might occur in the same wine). Malolactic fermentation, also known simply as "malo," is a secondary fermentation in which malic acids are converted into lactic acids. The result is a softer, smoother wine.

Extra contact with the lees is sometimes referred to as sur lie, French for "on the lees." The term "lees" refers to winemaking sediment: dead yeast, grape seeds and other solids. It might not sound like the yummiest stuff, but leaving the newly fermented wine in contact with the lees can add complexity and a richer texture. Sur lie is mostly noted on the labels of white wines, since red wines are commonly fermented with the grape solids regardless. Also, some winemakers will spend a lot of time stirring the lees to promote integration, a process called battonage in French.

—Dr. Vinny

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