At its core, wine is composed of water, alcohol, aromatic compounds, acids, and tannins. In this overview, we’ll take a look at what everything is and where it might come from. You might be surprised at some of the answers.
1.) GrapesWell, duh. Of course wines start with grapes, some even end with grapes, since the yeast needed to convert the grapes' sugar to alcohol is frequently found lurking on the skin of each berry. White grapes make white wines -- of course, white grapes are usually green or yellow, and some are even pink or red. Extremely few grapes actually have red flesh, so the color of the grape refers to its skin color. You can make white wines from red grapes, as well as Rose and red wine, of course.
2.) YeastThe yeast cells turn delicious, sweet grape juice into wine. They eat sugar and produce alcohol as a by-product. Many vineyards like to use indigenous yeasts -- those found on the grapeskins themselves -- as each vintage can bring a different combination of yeast strains, which may allow for more distinctive and complex wines. Most wineries, though, use cultivated, or commercial yeasts. There is a distinction, however: As some wineries find that a specific yeast that was indigenous to their vines produced a better than average result, the winery may begin to cultivate the yeast. Most wineries that use truly commercial yeasts use them because they are efficient and tolerant of high-alcohol environments (aka the Achilles' heel of many indigenous yeasts; it can lead to what are known as stuck, or incomplete fermentations.)
3.) AcidAcid is the part of wine that makes you smack your lips and leaves your mouth watering. It’s a vital component of deliciousness in wine. Acid is naturally occurring in all fruit, and we know from making lemonade that there is a subjectively ideal balance that can be achieved between sweetness and acidity. Even in a dry wine there are flavors that we can perceive as sweet (alcohol also can give an impression of sweetness), so having the right amount of acid in a wine is crucial. Grapes are born with primarily hard Malic and Tartaric acids, though many whites and most reds go through a secondary, bacterial fermentation (as opposed to yeast-driven) that converts the acid of green apples (Malic acid) to the softer acid of fermented dairy products such as yogurt (lactic acid). As grapes ripen, sugars increase and acids tend to decrease, so some winemakers routinely add additional acid to their wines. The most common acids used in acidification are Tartaric acid, Malic acid and citric acid. Some wines are also de-acidified by adding specific salts that can precipitate out tartaric acids.
4.) TanninsTannins come from the seeds and skins of grapes -- and stems, too if they’re added into to the fermenting must -- as well as from wooden barrels that can be used to age wines. The tannin in wines acts as a preservative and, along with acidity, is referred to as the structure of a wine. Tannins make your mouth pucker, your gums feel fuzzy, and your mouth feel dry. You can probably see already that having the right balance between drying tannins and mouthwatering acids is pretty important. The tannins in fruit and the tannins from wood are a bit different, but it’s hard to tell them apart and they pretty much do the same thing, so I’ll save that exercise for another time. Tannins can also be added to wines in powder form.
5.) AdditivesThis is the dirty truth about modern winemaking. There is a laundry list of additives, some with long historical roots, others recent additions to the winemaker’s medicine cabinet, all of which can be used to “improve” wines. Of course you might ask yourself why wines need so much “improving,” since for thousands of years folks have been making some pretty good hootch with just grapes and a bucket, but that’s a discussion for another day. Here's a brief rundown of what else might be lurking in your next glass of wine.
Enzymes are added to fermenting wine to help prevent the growth of bad yeasts that can cause wine spoilage. There are even enzymes that improve the formation of sediment in young wines, allowing for better filtering, and thus leading to higher yields.
Polysaccharides are added to promote the retention of color, tannin, and flavoring compounds extracted from grape skins.
Gum Arabic is added to wine to lock in the aromatic compounds in a wine, but it also adds a richness to the mouthfeel, which has become its main propose.
Sulfur products are used as a anti-oxidative preservative in wine. These are products that have long histories in winemaking, and are actually one of the wine additives that we’re seeing less, not more, of as winemakers develop a better understanding of what a sufficient dose of SO2 is.
6.) Fining agentsOnce upon a time wines were fined (think of it as filtering, but with the filtering drifting down through the wine as opposed to the wine being forced through a physical filter) with ox blood and egg whites. (Learn more about the ancient history of wine in our series on early winemaking practices.) While egg albumin is still a common fining agent, it has been joined by things like bentonite clay, gelatin, and even silica. There is no actual residue left from proper fining, so don’t look for chunks in your glass (sediment in wines is something entirely different, and we’ll talk about that next time.)
What makes a wine's structure?Tannins
Tannins come from grape seeds and skins, as well as from the oak barrels used to age wine. They give wine an astringent bite, and protect the fruit from oxygen.
Acid comes in many forms, but they all help give wine its mouth-watering zing. Red and white wines are sometimes treated differently to achieve proper balance.