Buzz: Hey Marnie, how do they make white wines out of cabernet grapes?

Marnie: They don't, Buzz. It's true that some white wines are made with grapes that look pale purple on the vine, like pinot grigio and gewurztraminer. Darker grapes, like pinot noir and monastrell, can be used to make white sparkling wines, too.

Buzz: Then why can't they make white wine out of cabernet?

Marnie: I didn't say it couldn't be done — just that it doesn't make sense. In the cases I mentioned, vintners separate the clear grape juice from the purple grape skins before any color bleeds through. These are both exceptions to the rule, though. But there's just no economic incentive to use the kinds of grapes that make the darkest red wines – like cabernet sauvignon and syrah – to make white wines because red wines command higher prices.

Buzz: Good point. But if cabernet sauvignon is worth more, how come they make so much of it into "sauvignon blanc"? That just means "white sauvignon" right?

Marnie: Yes and no. Yes, blanc is the French word for white, so you're right that sauvignon blanc does literally mean "white sauvignon." But, no, the sauvignon blanc wines you see at the wine store are not made with cabernet sauvignon grapes. Sauvignon blanc is a grape variety in its own right, a green-skinned fruit that makes bright, tangy white wines that are usually dry and quite refreshing. The two grapes share a family name because the two grapes are related. In fact, genetic testing has revealed sauvignon blanc to be one of cabernet sauvignon's parents.

Buzz: Weird. The wines couldn't be more different, yet they share the same family name.

Marnie: There is also a faint family resemblance in the flavor of sauvignon blanc and cabernet sauvignon if you look for it. It's hard to compare white and red wines, as their production is so different. But these two feature a leafy scent of green herbs in the background that adds flavor interest, especially when they're grown in cooler growing regions. It's harder to pick out in American wines, which tend to come from warmer areas.

Buzz: It's like the difference between using six cubes of sugar cubes here while the rest of the world uses two sugar cubes.

Marnie: If you're tasting the "white sauvignon" and the red one, it can help the wine stand out in a crowd. Taste examples from Bordeaux in France, where both grapes are native varieties, and get something special.

Buzz: Once again we reach an agreement. But can we get the  Daily News to send a few bottles to our readers?