The Malolactic Story

Malolactic conversion in wine is the softening of wine flavor by the conversion of the small amount of malic acid present in wine into lactic acid. Of course the largest acid ingredient in fine wines is tartaric acid which amounts to about 5 grams per liter, or 0.5% by volume. Even that small amount of acid is a key flavor component of wine. The second most common acid occurring naturally in wine is malic acid, only about half as much as the tartaric acid ingredient but still a critical taste element. With the action of a catalyst, malic acid (a somewhat harsh acid), converts to the more gentle lactic acid. Lactic is so named because of its presence in milk. This conversion of a harsh acid to a softer one is what gives Chardonnay wine the buttery flavor which I have always preferred and is now preferred by most other people as well.

When I studied winemaking at U.C. Davis in the mid 1980s I attended a lecture on how to prevent malolactic fermentation. I thought at the time the Davis course was not applicable to my winemaking. Instead of preventing the malolactic conversion, I wanted to encourage the process to improve the wine taste. In the next ten years, most people in the industry came to my point of view and the malolactic conversion, now better understood of course, is almost universally, employed. But, upon returning to U.C. Davis in the early ‘90s for a refresher course, instructors were still teaching how to prevent what they still refer to as “malolactic fermentation.” This illustrates that in the field of winemaking there is a certain amount of misinformation, including some from the famous University of California at Davis.

Davis has made enormous contributions toward the better understanding of vineyards and winemaking, but their record is not unblemished. They made one colossal mistake when they developed and promoted an XR1 clone rootstock which was widely planted in California. It had a known inherent susceptibility to phylloxera, the louse which twice in this century had destroyed the vineyards of France and California. Jarvis Vineyards along with most of the rest of Napa is in the process of replanting all our vineyards since phylloxera struck the Davis rootstocks.


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