There is a recurring item on the Wine Spectator Web site called "Ask Dr. Vinny". In it, the Spectator writers take on commonly asked questions about winemaking and wine consumption. Last month there was a question from a reader in the United Arab Emirates: "Is there any change that can be made in viticulture practices to produce low-alcohol wines apart from using reverse osmosis?"
I was pleased to see that the response included the obvious: "Want lower-alcohol wines? Pick sooner rather than later." You might think, "well, duh" but implicit in the question is a commonly-held reliance on the technological solution in the world of modern winemaking.
I've fielded several questions recently about a related topic: whether our wines go through malolactic fermentation. To understand what this means, please bear with a bit of science (or skip ahead, if this is old hat or if the thought of chemistry equations makes your skin crawl). Grape juice undergoes two different types of fermentation in its transformation into wine. In the first, and most dramatic, fermentation (typically called "primary fermentation") yeasts convert sugar into alcohol, carbon dioxide, and heat. This fermentation is the core one that turns grape juice into wine:
Sucrose (C6H12O6) ==> 2 Ethanol (C2H5OH) + 2 Carbon Dioxide (CO2) + energy
But there is another chemical reaction (technically a decarboxylation, not fermentation) caused by a family of bacteria that converts sharp-tasting malic acid into the gentler lactic acid and carbon dioxide:
Malic Acid (C4H6O5) ==> Lactic Acid (C3H6O3) + Carbon Dioxide (CO2)
Malic acid, commonly found in apple skins and the primary flavor in rhubarb, is an aggressive acid, with a pH of 2.21 at 100 mmol/L, while lactic acid, commonly found in milk products, is gentler, with a pH of 2.44 at the same concentration. That difference may not seem like much, but because pH is a logarithmic scale, a liquid with a 2.21 pH has 70% more acidity than one with 2.44 pH. An image of the process (courtesy of Wikipedia) is to the right.
OK, enough with the chemistry. In practical terms, while all wines go through primary fermentation, only some go through malolactic fermentation. It's pretty easy to understand why you would want a wine to do so: it produces a creamier texture and smoother mouthfeel, as long as there are enough other acids in the wine to maintain balance. Red wines nearly always are let go through malolactic; they contain much higher levels of tannic acids from the skins of the grapes since they are fermented with the skins, while most white wines are pressed first and fermented separately. These tannic acids tend to be highlighted in an unpleasant way by malic acid, while the lactic acid produces a softer, richer, more appealing mouthfeel.
Why wouldn't you want a richer mouthfeel on whites, too? Well, it comes with some costs, when grapes are super-ripe and therefore lower in natural acidity. Historically, nearly all whites did go through malolactic fermentation, because the technology to stop the process (typically some combination of sulfur dioxide addition, refrigeration, and sterile filtration) hadn't been developed yet. But as these techniques came into relatively widespread use, some winemakers chose to block the malolactic fermentation on whites with sweeter or more floral profiles, where brighter acidity was a desirable foil to the wine's character.
And so things stayed, until recent years when the trend toward riper and riper wines left the stopping of malolactic fermentation as a standard practice for many winemakers. Leave the grapes on the vines for another couple of weeks, pack extra rich and tropical flavors into them, then stop the malolactic fermentation to give a balancing dash of acidity to an extravagantly rich wine. Sure, you end up with a lot of alcohol, but if you're trying to make the biggest, most impressive wine, and don't want it flabby, it's a relatively easy choice.
What's the problem with this? Well, it's in the eye of the beholder. For many people, nothing. But I find that the extra ripeness and alcohol typically mask expression of the soils, and abundance of power with often disconcertingly elevated acidity makes for wines that are fatiguing rather than refreshing. It's like the trend toward IPA's with extra hops, extra malt, and extra alcohol. Sure, they're impressive, but I rarely finish even my first glass, let alone order a second. More isn't necessarily better. In this, I realize I'm out of step with current trends. So be it. I'm still waiting for the artisan lager revolution to start.
Is stopping the malolactic fermentation always bad? Of course not. There are times when it's the right choice on a particular lot or in a particular vintage. We've done it from time to time, though not in the last five years or so. But picking earlier, when you have enough natural acidity that you can let malolactic go through and still have wines with balance, seems to me to be much more desirable. The wines are more expressive, less alcoholic, and show an appealing, creamy texture that seems to show off our limestone soils.
To choose another analogy, I'm finding myself, more and more, seeing white wines with high alcohol, intense tropical flavors and lots of malic acid as the equivalent of a celebrity who has had too much surgical enhancement. The net result often isn't beauty, and can border on the grotesque. You can have Pamela Anderson. I'll take Gwyneth Paltrow.