The Science Behind a Great Bottle of Wine
What you taste and enjoy is a result of what your high school teacher was trying to get you to understand
If you remember anything from your high school science classes, your teacher spent time instructing you on the two main transformations that happen in our world. Things either undergo a physical change or a chemical change.
Both processes happen to wine. There’s an amazing amount of science that occurs in the gorgeous glass of wine you’ll enjoy this evening. Here are a few highlights.
Temperature: Physical Change
We usually only think of temperature when preparing to drink wine. We want our white wine chilled, and our red wine at room temperature. From a science standpoint, during the fermentation process, the actual temperature of the wine is less critical than the stability of the temperature.
The optimal storage temperature of wine is about 55 degrees. Any fluctuation will cause the wine to contract or expand. The glass bottle is a constant, but expansion or contraction of the wine due to temperature fluctuation increases or decreases the pressure in the bottle.
The cork doesn’t make a completely airtight seal. The expansion will force some of the wine’s bouquet to escape through the cork. Contraction pulls a slight vacuum, pulling air through the cork and causing oxidation. This is what can ruin the wine. A certain amount of oxidation is what mellows wine, but too much oxygen pulled into a wine bottle because of fluctuating temperatures will destroy the wine.
There is science behind the serving temperature of the wine, as well. Chilling wine helps to accentuate its acidity. White wines tend to have acidic flavors, so chilling it helps to present the character. Chilling a wine promotes the flavor contributions of tannins. These are in the seeds and skins of grapes, and red wines often are crushed with both. A chilled red wine becomes less appetizing because of this.
Fermentation: Chemical Change
Yeast eats the natural sugars in grapes during the fermentation process. The result is carbon dioxide, alcohol, and more than 200 aromatic esters. The combination of these three things is what gives each wine its unique characteristic and flavor.
Those esters are extremely important. Each has a unique and familiar taste and feel on our tongue, and our brains create associations with them. It’s why when you smell an onion you can easily recall its taste and texture.
You’ll often hear how a white wine has a note of green apple, or a red wine has a note of tobacco. Many of those 200-plus esters in wine have previously-established associations. The aroma or taste of wine triggers that alternate association.
All of this takes place as the wine ferments. Sometimes this begins in oak barrels or even large stainless-steel vats. It continues after the wine is bottled.
Terroir: Physical and Chemical Changes
Wine made of grapes from a particular place will possess the characteristics associated with the physical environment where the grapes were grown. It’s why most wine stores sort what they sell by region.
There’s more than geography making up a wine’s characteristic. Additional factors include weather and rainfall, as well as soil conditions and other factors that have a physical impact on the grape vines and the fruit they produce.
Collectively, this is known as “terroir.” It causes a great amount of debate, mainly because there’s little agreement on exactly how much these physical things impact what you end up tasting when you drink wine. Some winegrowers have begun to use the concept of terroir—specifically the impact of rain—to apply stress to a crop by limiting irrigation. Their hope is to increase the production of aromatics in the grapes, which should manifest as a deeper body in the wine.
Something no one debates is the science-based impact that climate has on grapes that become wine. Climate impacts grapes the same way it does any harvested produce. A warmer temperature will produce a riper fruit.
When grapes ripen, the amount of sugar they produce will increase. We will perceive it to be less acidic when we drink the wine made from these grapes. So, you’d think that wines produced from grapes grown in warmer climates would produce sweeter wines.
This turns out not to be the case—and it takes us back to a chemical change. When these grapes with higher sugar content begin to ferment, the yeast has more sugar to consume. The result is a wine that’s higher in alcohol, with a less acidic taste. And, it’s why white wines tend to have a higher alcohol content than red wines.
Science continues to happen in your glass
It’s estimated that a glass of wine can contain thousands of different chemical compounds. They’ll continue to interact and cause changes as the wine is exposed to the air and its temperature changes. Even the shape of the glass can affect what you taste and smell. This is especially the case with bubbly wines. They release unique aromatic chemical compounds when their bubbles burst.
Fluctuations in the concentration of these chemical compounds can make noticeable changes, too. Science has identified one compound known as 3-isobutyl-2-methoxypyrazine. Isolated, it tastes like green bell peppers. You definitely would not like a wine if this particular chemical compound was too pronounced. Grapes grown in full sun have been found to produce less of this compound.
If you know even just a little bit about wine, you’ve come across the concept of tannins. Your brain may have even made an association with the bitter edge you taste from over-brewed tea. People often say that red wines with a high tannin content make their mouthfeel drier after they’ve taken a sip.
Science can explain this. Tannins bind to the proteins in your saliva. We appreciate tannins in our wine because they help to give the wine a long aftertaste. We wouldn’t appreciate it if the tannin level is too high, though. Scientists theorize that grapes developed tannins in the skin and seeds as an evolutionary tactic to prevent animals from eating the fruit.
We usually think that an amazing glass of wine is due to the artistry of the winemaker. He or she is actually more of a scientist. They leave art up to whoever has been hired to create the label.