Grapes (specially, grapes of the species vitis vinifera) are the stuff of wine. They’re little spherical wonders that have produced some of the world’s most unique, historic, culturally significant beverages for thousands of years. Thousands. As such, we think they deserve a closer look. What about a grape makes good wine?
If you’re a red wine lover, this is where your two best buds, color and tannin, hang out. It’s true that white grape skins (and pink grape skins, as in the case of Pinot gris, for example) contain color and tannin too, but for the sake of simplicity, we’ll concern ourselves with what the skin means for red wine.
Aside from keeping all the good stuff in and all the bad stuff out, the skins of the grape are largely responsible for the structure of wine, because they’re the keepers of the tannins. Tannins are what give wine that textural grip and contribute to (ugh) mouthfeel. Good winemakers know what to do to extract the largest (or smallest) amount of tannin from the skins depending on what style of wine they’re going for. They do this by controlling how long the grapes are allowed to macerate — or, sit in a fermentation vessel — and how gently the grapes are pressed after maceration. Maceration and crushing are both processes that allow tiny little particles of grape skin to release into the grape juice; the quicker the maceration and the gentler the crush, the less tannin-loaded the resulting wine, and vice versa.
So, if the winemaker’s going for a powerful, full-bodied style (think Châteauneuf-du-Pape), those grapes might be left to ferment and macerate, juice and skin together for several weeks. They might be stirred around a lot (a process called remontage), either by hand or mechanical pump, to help encourage little bits of grape skin (and, thus, tannin) to integrate into the juice. When the winemaker decides the wine has enough stuffing, everything gets run through a press and the juice is allowed to mature before bottling. Want to make white wine from Pinot Noir à la Blanc de Noirs Champagne? No problem. Put those grapes in a gentle pneumatic press, grab your juice, put it in a tank to ferment and toss the skins in the compost. The longer you let the skins fraternize with the juice, the more color and tannin the wine will exhibit in the end. (As a general rule, color and tannin tend to have a corollary relationship, since they both come from the same ‘hood.) Those little micro particles can also be removed after vinification through fining and filtration, but it’s generally better when they’re anticipated and controlled from the get-go.
The flesh of the grape, as you might guess, is the jelly-like stuff beneath the skin — sweet, juicy stuff. It makes up most of the grape and, thus, most of the “stuff” of wine. A lot of that stuff is just water, however, so the skins and tannin, thin as they are, usually have a little more influence on the resulting wine than the flesh itself, especially in the case of red wines.
What does the flesh give wine, then? Mostly, winemakers are focused on two opposing things that exist simultaneously: acid and sugar. Acid comes from phenolic compounds found in the cells that make up the flesh, and sugar — just as with all fruits — increases with ripeness. Moderate-to-high acid content is what would make you, the wine lover, think of a wine as refreshing, bright, clean and fresh (think lemonade and/or Sancerre). Low-acid wines might be described as creamy, soft and round (think Napa Chardonnay). Acid content gives wines structure, texture and balance.
Sugar’s a little less cut and dry. While the sugar content in the grape’s flesh can result in a sweet wine, most winemakers are concerned with how it will affect the wine’s alcohol content. The higher the sugar content in a grape, the higher the potential alcohol content, because fermentation is basically yeasts eating sugar and pooping alcohol. As long as those little guys can eat sugar, they’ll keep producing alcohol, and the wine’s ABV will keep creeping up. Start with grapes without a lot of sugar in their flesh, however, and the yeasts won’t last too long, giving you the perfect wine to drink at brunch.
Stems and Pips (a Cuter Name for Seeds)
Together, the stems and pips of the grape, along with the skins, form a trifecta of potential tannin. Unlike skins, though, it’s possible to avoid involving the stems and pips more or less altogether, if desired. Because stems and pips don’t ripen like skins do, winemakers are often quick to keep them out of the equation, since they both contribute a potentially unique astringency to the final wine that not everyone digs. If you’ve ever gotten a mouthful of grape seeds, you know how their bitter, “green”-tasting astringency can overload your palate.
Unlike table grapes, vitis vinifera don’t come in a seedless variety, and though that green tannin can be desirable in certain wines — especially those meant for aging, as it can act as a preservative and lend complexity over time — it’s not always what the winemaker is setting out to achieve. Remember the gentle crush? That soft pressure will help keep the seeds intact and the tannin at bay. Stomp on those suckers, though, and all of their bitter, astringent glory will be released into the grape juice, too. Likewise, stems are often removed even before maceration, giving the winemaker a chance to avoid their contribution to the process altogether. Generally, wines that are made from grapes that have been de-stemmed and crushed gently are more fruit driven, with softer tannin and fewer herbal notes. Wines made with all the goods tend to be more powerful, structured and earthy.
Wait. Where Does the Flavor Come From?
Unfortunately, it isn’t that easy. Every part of the grape contributes to the wine’s resulting aroma and flavor. Grapes are chock-full of phenolic compounds (the things that make things smell like other things), so they’re little vessels of scents and flavors just waiting to do their thing with the right handling. Things like geography, climate, soil type, growing conditions, rainfall, harvest method, wild and cultivated yeasts, length of fermentation, maturation vessel, post-fermentation tinkering and bottle age all have a hand in what you smell and taste. Ultimately, though, it’s a sort of magical combination of the health of the grape and winemaker’s skill that will give a wine a more remarkable presence in your glass.