What’s in Wine?


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An endless array of aromas and flavors and, yes, that little buzz we get – these things make wine a special beverage. But what’s truly beguiling about wine is how directly it comes from nature. Wine isn’t so much made as it is guided into existence. Wine wants to be.

The key is what’s in the grapes. They’re a readymade package for the production of wine.

Going Inside the Grape

More than 70 percent of a grape is made up of water. This is why we drink wine instead of eating it with a spoon. But it’s the other key components – sugars, acids, volatiles and phenolics – that come together to really make wine grapes unique to their task.

With a few exceptions, wine grapes come from a plant species called Vitis vinifera, a vine that originally grew wild in Transcaucasia, around the Mediterranean Basin and into Western Europe.

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Vinifera grapes cultivated for wine production accumulate more sugar than most grape species, like Vitis labrusca, the native American species that includes the Concord variety. The amount of sugar in grapes is measured in degrees brix. This isn’t a bad term to get to know: Hang around a winery and you’ll hear winemakers talk about “brix” a lot, especially around harvest. It’s actually a measurement of soluble solids in a liquid, but since almost all the solids are sugars, brix is a good stand-in for sugar level.

Whereas your Concord grape might come in at 15 brix, ripe Chenin Blanc will be around 24 brix, which will convert nicely to around 13 percent alcohol when made into wine. And at the same time, the Chenin will have a mix of acids – mostly tartrate and malate – that will balance out the sugars. Those acids will also help produce a wine with a pH between 3 and 4, low enough to provide some protection against spoilage.

Variety Is the Spice of Wine

Still, not just any Vitis vinifera grape will make a fine wine.

This is where variety comes into play. Variety (or cultivar, as it’s sometimes known, though the two terms have slightly different meanings) comes down near the end of the line in taxonomy, after species. Merlot, Syrah, Chardonnay – these are all varieties of Vitis vinifera. Note: they aren’t “varietals,” which are wines primarily made with, and identified by, a single variety.

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Thompson Seedless is a vinifera variety that can get plenty sweet and ripe, but you’ve never bought a bottle of Thompson Seedless wine. That’s because the grape just doesn’t have the flavor components to stand on its own as a wine (though it is used to fill out lower-end wines). The skin, where much complexity resides, is thinner and the grape is larger, leaving the pulp less concentrated with the volatiles and phenolics that bring flavor.

Grapes Into Wine

With all these good things, it doesn’t take much to turn grapes into wine. All they really need is a yeast, the organism that converts sugar into alcohol and carbon dioxide.

Winemakers often add a yeast selected especially for fermentations, but a fair number don’t; yeasts are everywhere around us, including in vineyards and wineries. With their high levels of sugar and plenty of nitrogen nutrients, grapes that are simply crushed will turn into wine. It can be a little riskier doing it that way, because some yeasts can produce off flavors and aromas, but plenty of winemakers make it work.

From there, what goes into wine is really a question of style and fine-tuning. In some cooler Euepean regions, there’s a long tradition of adding sugar to boost alcohol levels. In warmer regions, a touch of tartrate might be used to improve acidity. And almost certainly a winemaker will add sulfites. Levels today are lower than ever before, but this time-honored technique for preserving wine is nearly universal.

Even when a winemaker doesn’t add sulfites, there will be some in every wine. That’s because sulfites, in small amounts, are a naturally occurring byproduct of the fermentation of grapes – those amazing grapes!

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