If you have ever wondered what exactly is in your glass of wine, you're not alone. Many people know they love to drink wine, but they don't know much about the actual chemical complexity in the bottle. The label may have pretty artwork and list the alcohol content, but it does you no favors when trying to figure out what exactly is in each sip. So, what's really in wine?
Grapes are primarily water and sugar, with small amounts of carbohydrates, various acids, phenolics, and minerals. A typical wine contains around 85% water.
The alcohol percentage is one of the few components listed on the label. Referred to as ABV or alcohol by volume, it varies depending on the grape, climate, and winemaking practices. Usually though, wine is in the range of 10-15% ABV. The alcohol is produced in the process of fermentation, when yeasts consume the natural sugars in the grape juice and produce ethanol and carbon dioxide. Some sweet wines stop fermentation early to keep some of the sugars. In this case, they have an even lower ABV, around 5-7%.
Glycerol is a natural product of fermentation, and it makes up about 1% of wine. While technically alcohol, it has less effect on your nervous system and more effect on how you perceive the mouthfeel and body of a wine. This compound is partially responsible for forming legs or tears on your glass, bringing viscosity and texture to the wine.
Similar to alcohol content, the acid in a wine can vary, but it is typically around 0.5% acid, with a pH between 3 and 4. There are a few types of acid in wine, with the main three being tartaric, malic, and citric. Acid helps to bring brightness and balance to a wine. The malic acid in grape juice is quite harsh and is often converted to a smoother, rounder lactic acid in the process of malolactic fermentation.
Carbohydrates or sugars are present in wine to different degrees, making up about 0.4% of wine. Naturally occurring fructose and glucose are in grapes (and therefore grape juice) prior to fermentation. During the process of fermentation, yeasts consume those sugars and convert them to alcohol. If sugar remains after this process, it is referred to as residual sugar. The residual sugar in wine is measured in grams per liter (g/L). Unless you are drinking a dessert wine or port, your wine is likely pretty dry, containing between 0-10 g/L of carbohydrates.
Phenolic compounds are a small, yet mighty, part of wine. They only make up around 0.1% of wine, but they play a part in both color and taste. Pyranoanthocyanins are responsible for giving wine its color through interactions with other compounds. Flavonoids are another group of phenolic compounds; they are responsible for the tannins in wine that provide structure, astringency, and bitterness.
Esters, Lactones, Thiols, Terpenes, & Pyrazines
Finally, what gives a wine a unique aroma and flavor profile are the esters, lactones, thiols, terpenes, and pyrazines that are present in the grapes or created during the fermentation process. A wine can contain over 200 unique esters that can be fruity, floral, or herbaceous. Think strawberry, rose, and jasmine. Lactones are a type of esters that impart creamy, buttery flavors like caramel and vanilla.
Thiols contain sulfur and therefore must be in careful balance in a wine so as not to produce strong aromas of cooked cabbage and rotten eggs. When present in small amounts, thiols impart aromas and flavors of gooseberry, passionfruit, and guava. Terpenes are essential oils. They typically impart aromas of lavender, lychee, eucalyptus, basil, marjoram, and thyme. Pyrazines are responsible for some of the greener aromas in wine such as bell pepper, herbs, olives and elderflower.
What Shouldn't Be in Your Wine
While it's easy to think that wine is simply fermented grape juice, that is far from the case with industrialized commercial wines. The reality is that the U.S. federal government allows for over 72 chemical additives to be used without making note of it anywhere on the label or tech sheet. Some of these additives include food coloring to correct for color, fish bladders to strain out yeast particles, and more acid or sugar to correct for taste.
Long story short, wine can be highly manipulated without a transparent window to account for what's in the bottle. So how do you avoid all the chemical additives? Search out natural wine. The premise of natural wine is that it isn't highly manipulated. Natural winemakers are also often much smaller and more transparent than their commercial counterparts.
Knowing What's in Wine
So now that you know what is in wine naturally, search out wines that are expressive reflections of terroir to enjoy it at its most basic chemical makeup.