What if someone told you there was a substance you could put into a red wine that made the wine darker than you could get naturally, covered pyrazine and masked some elements of brettanomyces, added a textural element that made the wine "sweeter" in the finish and was reliable because it made even mediocre wines taste more uniform. Would you use it?

Apparently, thousands of winemakers around the world have answered this not-very-theoretical question in the affirmative. In interviews with a dozen winemakers and wine company executives, I learned that such a substance does indeed exist. Sounding much like a magical potion that improves many wines into which it is blended, Mega Purple (and its cousin Ultra Red and other similar products) are thick concentrates derived from Teinturer grapes, and are aimed strictly at filling gaps in red wines that have color deficiencies, a procedure that otherwise might be accomplished by blending in a darker wine.

Assume you have a Syrah that for one reason or another finished fermentation with a paler color than you believe to be desirable. (Assume the wine is aimed at the $30 price range, and that its color seems to indicate the wine is lacking in flavor.)

In the past, winemakers would use a dash of Petite Sirah or some other dark red wine to "plump up" the color. (A dollop of Alicante Bouschet has been used often for this purpose.) Now, instead of having to go to the extreme of buying a small amount of such wine from the bulk market, wineries are resorting to Mega Purple, which sells for about $135 a gallon.

That sounds expensive, but the substance is highly concentrated and a little goes a long way.

If you haven't heard much about Mega Purple, there's a good reason. It flies below the radar intentionally, because winemakers are reluctant to discuss their use of it. Indeed, many of them feign surprise that it even exists, though in face-to-face meetings with some of them, the reactions are nearly comical. "Mega-what?" one asked, with a faux-perplexed look and a sly grin.

The reasons they seem reluctant to mention it are many. A couple of them said, confidentially, that to admit using such an additive implies that their grapes are less than superior. That is, if a concentrate is appropriate for a wine, clearly their grapes are somehow deficient. And thus, the wine isn't "fine wine."

Two other winemakers admitted that they rely on Mega Purple only for those wines that somehow are a bit deficient in one area or another, and that they use only tiny amounts, but that their winery owners are fearful of revealing that such a substance ever crossed the winery's threshold.

Yet one Monterey County winery president confided, "Virtually everyone is using it. In just about every wine up to $20 a bottle anyway, but maybe not as much over that."

Another, a long-time Sonoma County winemaker, said, "Sure, I use it, but only very infrequently and only for some of my (lower-priced) wines. Look, Mega Purple has residual, so it adds a bit of texture, and that adds a little weight and it pops the fruit."

He said he uses no more than .06% of the final product. "Over that, and you run the risk of getting some over-ripe characteristics."

The Monterey County winery executive said, "You don't want to go above .2%, so you're below the sweetness threshold." He said his winemaker knows that "when you get it up to .3%, .35%, you're going to smell it. And at .45%, (the wine) comes out really sweet."

Mega Purple is produced by Constellation and sold by third-party vendors. It is made by concentrating the Teinturer grape Rubired, a cross between Alicante Ganzin and Tinta Cão. As such, say winemakers who use it, the concentrate has a distinctive aroma that smells a bit like what they called "Central Valley red," with hints of a foxy sort, not unlike a native American grape.

Napa Valley winemaker Scott Harvey was fascinated by Mega Purple. In an interview he said: "I don't use it, but any winery you talk to will say they don't. One reason I don't like it is it has a distinctive flavor to it that I think is identifiable.

"So you can see what's wrong with using it. If everybody uses it, they're adding the same flavor." Harvey said that if Napa Valley Cabernets are being criticized for having an over-ripe character, "I suspect part of that is Mega Purple, sort of a jammy taste, but with no fruit to it."

Harvey said he tested Mega Purple and noted, "It has a kind of richness, a kind of weight to it, and it's kind of, like, syrupy--that flavor you get from some (hot climate) Alicante Bouschet. Well, I'm getting sick of it. I wanted to get some pyrzines in my wines, and this (Mega Purple) seems to wipe out that character."

Winemaker Clark Smith, founder of Vinovation, a wine analysis and consulting firm in Sebastopol, Calif., said, "Sure, I'll admit to using it. It touches up color, and I think when it's over-used, it makes the argument that's in 'Mondovino,' that structure can interfere with, or cover up, regional character."

Smith said he uses Mega Purple only for wines that are truly deficient in some aspect that the concentrate would fix, but because it has 68% sugar, Smith believes that it is best used when added before fermentation, so the sugar ferments out.

Harvey added that if the product is used at all after fermentation, "you have to sterile filter the wine."

Smith added that he's aware of the drawbacks of using Mega Purple, especially in larger amounts. "Mega Purple has a way of homogenizing flavors and aromas," he said. "And that's a danger.

It shifts wine flavors toward the same thing, and that makes wines very similar to one another. You don't want the book you read this week to be the same as the book you read last week, do you? So shouldn't wines offer different characteristics, too?"

Smith said he once made a Pinot Noir that was very light in color, but had an attractive perfumey aroma and loads of minerality, "nothing like an American Pinot. And there was a lot of pressure to make it fleshier and darker, more acceptable to the expectation of Pinot coming out of California.

So we used a little bit of Mega Purple, and when we got to the point at which it got in the way of the flavor profile of the wine, we backed off.

"The key question there was, 'Do you want it big and stupid or do you want to see the richness of the wine?' You just shouldn't use too much of it."

To test what Mega Purple does to wines, I asked Scott Harvey to stage a blind tasting of two of his wines that had been "adjusted" with both Mega Purple as well as another red additive. Harvey added large amounts to two of his 2004 red wines (a Cabernet Sauvignon and a Zinfandel), ranging from .2% to .8%, four levels for Mega Purple and four for Ultra Red. He then put two control glasses in among the 10 glasses and a panel of judges ranked the wines.

Tasters included John Buechsenstein, winemaker and UC Davis instructor in sensory evaluation; winemaker Kerry Damskey; Harvey; Smith and Dr. Richard Peterson, former winemaker at Beaulieu and long a fixture in the California winemaking scene.

The "additive" wines were clearly plumper and a bit more full-bodied than were the control samples in both cases, and they seemed to work best in the Cabernet Sauvignon. The Cabernet in this case wasn't very dark in color, so the additive wines bolstered the red color, but even at the lowest levels, I found the wines to be a bit fatter and less characteristic of Cabernet. For me, the Zinfandels were most hurt by the Mega Purple, because the color additives compromised the varietal spice.

Most of the comments from the tasters were interesting, noting that they could see how a winemaker would choose to use an additive to improve the color of a color-deficient wine, but all said that the use of such elements is very tricky.

Damskey said he has used Mega Purple in the past a couple of times, "but the addition has to be a lot less" than we used in our blind tasting. "And you have to be very careful how you use it. The downside is that I don't like the way it changes the aroma. More often than not, it mutes the aroma."

Peterson, however, said he could see how a wine might be improved a bit if Mega Purple were added, notably a wine without much flavor development. He actually liked a few of the additions he tasted. "I liked the softening effect that the sugar adds," he said.

Harvey pointed out that in some of the wines with the additive, "the 'sweetness' in the Cabernet made the tannins more astringent," because, he said, the sweetness was out of sync with the rest of the wine.

"There's no question that (Mega Purple) adds a fruit component all its own," Smith said. "If you can do it transparently, then fine. But winemakers should ask the question--'Are all my wines aimed at the same thing? Do I want them to taste pretty much like each other?' If not, then they should be very careful about using it."

"In my trials," Damskey said, "high levels, such as these, didn't work at all. Even in lower-level red wines, there is a jammy, over-ripe component. And despite the fact that there's more sugar there, you tend to lose that delicate 'sweetness' that grapes give you. At lower levels, I think the sweetness brings something to the table."

He said the downside to using it is that the winemaker loses some aromatics and the varietal nature of the wine is a bit compromised. He said he would never go over .1%, and more likely would use it at levels of .06% or less.

Smith said, "I think it's ridiculous to add residual sugar to red wine. And this (Mega Purple) seems to give the wine a jugy, tooty-fruity aroma. And it changes the texture. I didn't like the parching quality of the tannins. And it also seems to cover some of the terpenes and thiols that are attractive in wines."

Buechsenstein said he was mainly surprised at how the additions at .2% and .4% changed the mouthfeel of the wines, softening in one way but making the tannins seem awkward and out of place.

Harvey added, "I don't plan on using it. It's easier to add Cabernet Franc to Cabernet Sauvignon. Using (Mega Purple), the wine seemed too disjointed, plus I got a sort of licorice or jug character from it."

One winemaker who said he used it once was John Williams of Frog's Leap, who said he dislikes "all the crutches that winemakers have come to rely upon, instead of working on what they should be working on--which is not irrigating the vines."

The only time Williams used Mega Purple, he said, was some years ago when he added a tiny amount to a rosé wine. "The wine didn't have much (pink) color, and it worked fine to bump up the color." But his addition was so small, he said, that it didn't alter the wine's aroma or flavor.

Williams' concern, he said, is that color additions like Mega Purple might someday "become part of the regular winemaking regime."

(Dan Berger has been a wine columnist since 1976. Currently he issues weekly wine commentary, Dan Berger's Vintage Experiences and a nationally syndicated wine column. His books include Beyond the Grapes: An Inside Look at Napa Valley and Beyond the Grapes: An Inside Look at Sonoma Valley. To comment on this article, contact him through edit@winesandvines.com.)