What’s the difference between Tannins and Acidity?
This one stumped me for a while. When you read about wine-especially red wine–you invariable hear some mention tannins and acid. What’s the difference? I wondered. I thought tannins were acid. At least, that’s what the dictionary says…. (See below) So, I decided to do a little research on the matter.
1. What Are Tannins?
“Tannin: 1. Tannic acid. 2. Any of various chemically different substances capable of promoting tanning.” The American Heritage Dictionary.
“Tannic Acid. A lustrous yellowish to light-brown amorphous, powdered, flaked or spongy mass having the approximate composition C76H52O46, derived from the bark and fruit of many plants and used in tanning, as a mordant, to clarify wine and beer, and as an astringent and styptic.” The American Heritage Dictionary
Okay, so we have a definition. But is it the right one when we’re talking about tannins in wine?
The answer, come to find out, is yes and no. Here’s why.
a. Hydrolyzable and Condensed Tannins
Tannins are a group of phenol compounds found in plants, which create a group of chemicals called “Polyphenols“. These polyphenols are, for the most part, soluble in water.
There are two main types of tannins: Hydrolyzable Tannins and Condensed Tannins.
Tannic acid is a particular type of hydrolyzable (basically means that it is able to be split up and broken down by interacting with water) tannin commonly found in the bark and wood of oaks and other plants. It is used commercially in tanning leather and in certain dying processes. So, what type of tannin comes from the bark of oaks and other plants? Hydrolyzable Tannins.
Another type of tannin, which is a non-hydrolyzable tannin, is called Condensed Tannins (also called “Proanthocyanidins”, but I like “Condensed Tannin” better, don’t you?). Condensed Tannins are often found in other plant sources such as tea, pomegranates and grape seeds and grape skins.
Hydrolyzable tannins and condensed tannins are the two main categories of tannins delineated.
b. Why Tannins tend to be in Red Wine
In general, the reason why red wine has tannins and white wine usually does not, is because red wine is made from red or purple grapes that are fermented with the seeds, skins and often pieces of stems1, which in turn give red wine its condensed tannins. White wine, on the other hand, is usually fermented with just the crushed juice from white grapes or skinless red grapes.
However, if a red or a white wine is later aged in oak (or other type of wooden) barrels, then a secondary source of tannin can be derived from the barrel as well. The type of tannins found in oak or other wood are the hydrolyzable tannins discussed above. It might even pick up some tannin from a cork as well.
c. Why are Tannins Important?
Tannins are very important to red wine. They provide color, flavor and structure to a wine as well as acting as a preservative. Often, wines with heavy tannins are meant to be aged or “cellared” for some time. As the wine is cellared, the tannins tend to mellow out while enhancing the wine’s body and flavor.
d. How do Tannins Taste?
Tannins are often described as bitter, puckery, drying, astringent or akin to the sensation of rubbing a swab of cotton down your tongue. I actually tried this and did see a connection between the two sensations. The flavor of tannin has also been described as the flavor of steeped black tea. (Which also has a high tannin content.) I tried this, too, and found the comparison very helpful in understanding the sensation and taste of tannins in my wine.
e. Summary on Tannins
In summary, while tannins in your red wine will have some acid property (because you will most likely have hydrolyzable tannins in there), the major effect of tannins in your red wine is the astringent or drying/puckery effect. The small amount of tannic acid that may be present due to barreling or corking will not be significant.
The effect of tannins in your red wine may further be noticed when they interact with certain foods rich in protein and fat (such as meats and cheeses). This is because the tannins will bind to and precipitate (basically means to draw out and form) certain proteins. When tannins do this-by precipitating and binding to the proteins in food-it actually can keep the protein from being dissolved as it normally would by your saliva. In this way, tannins also give body and structure to the wine by adding this effect in your mouth. Tannins give the wine a thickness and density that it would not otherwise have.
Some red wines, such as Cabernet Sauvignon or Shiraz, have more tannin content than others (such as a Pinot Noir or Merlot). If you do come across a wine that tastes very tannin-laden, try eating some food such as cheese or something equally meaty and hearty as it will have an effect on your taste of the wine as explained above.
So if the small amount of acid in tannins aren’t what wine tasters are referring to, then what are the other acids in wine?
2. What Acids are in Wine?
a. Types of Acids in Wine
There appear to be four predominate types of acid found in wine: Tartaric Acid, Malic Acid, Lactic Acid and Citric Acid. These acids add what is called “structure” and help shape the flavors and aftertaste (also called a wine’s “finish”). Acids also act as a preservative.
Another acid-Acetic Acid (vinegar)-is usually present in only trace amounts and contributes to a sweet/sour vinegar taste. Too much acetic acid in wine is not a good thing and can often be detected in super duper cheap table wines. Yeck.
Both tartaric and malic acids are produced naturally in both red and white grapes as they mature. As the grape continues to mature, the acidity level declines. In cooler climates, higher levels of tartaric and malic acidity tend to be present in grapes while warmer climates have higher levels of sugar, and thus, less acidity. In general, this is because, in warmer climates, the warmth and sunlight help grapes to mature much more quickly than those in cooler climates, thereby causing the grape the loose acidity at a faster rate.
b. Why Acid is Important in Wine
When a wine has too little acidity, it is often described as “flabby” or “flat” and is thought to lack structure. In short, it’s boring. When a wine has too little sugar and too much acidity, it is often unpleasantly tart and sour tasting.
Wine acids also affect the actual color of the wine. In red wine, the color signifying the most acidity is bright red. As the color mellows to purple then bluish tones, the acidity mellows with it.
Similarly to tannins, acids in wine can effect a wine’s color, they always effect the wine’s flavor and structure (as discussed above) and they also act as a preservative.
c. What Do Wine Acids Taste Like?
While tartaric acid appears to be the predominate acid in wine, not much mention is made of its actual flavor. One website described it as “crisp” and “acidy”. Um, thanks.
Malic acid, on the other hand, is frequently described as overly harsh, sharp and with a green taste like an unripe apple. Because malic acid has such a strong impact on the flavor, it is often softened by undergoing a process called Malolactic Fermentation (“Malo”) whereby the harsh malic acid is changed into a softer, smoother, butterier lactic acid that is said to be softer on the palate.
Almost all red wine goes through malo, while with white wine, it is simply up to the winemaker’s taste.
Citric acid can also be added to a wine to give it a sharper, more “citrusy” taste. I know, that’s about as helpful as the tartaric acid description. Sorry. From what I’ve read, it seems that citric acid is often used by home winemakers who want to add a bit more kick to their wine. I have not seen as much comment on citric acid as I have on tartaric and malic acids.
3. In Summary: Distinguishing Tannins from Acidity
When distinguishing tannins from acidity, it is easier to start by comparing a white wine that has not been aged in oak (perhaps a Riesling-it is usually quite high in acidity) with a deep red wine (perhaps a Cabernet Sauvignon from California or Australia).
When you try the white wine, you’ll notice the tart, zingy flavor that makes your tongue salivate a little. Kind of like drinking orange juice.
When you try the red wine, you might have that tart, zingy feeling, too (the acid), but what you’ll also notice is that drying, puckery feeling that seems to roll down the middle of your tongue and coat your mouth. The wine feels deep and … complex. That’s the tannins in the red wine.
Just reading about the differences might be helpful, but really, experimenting would be even better. Try a white wine with a red wine. Drink some stepped black tea, too-I bet it will help you more than any description.
You can get an even better feel of the difference by comparing a red wine with high tannins and lower acidity, such as a Cabernet Sauvignon or Shiraz (Yellowtail Shiraz from Australia is a good example–not expensive) with a red wine with lower tannins and higher acidity, such as Valpolicella from Tuscany (Bolla creates an inexpensive version that you should be able to find in your grocery).
When you drink the Shiraz, you’ll notice your tongue feeling gripped with that dry, puckery, steeped tea flavor and the wine will seem very dense and thick. When you drink the Valpolicello, it will feel much lighter and crisper and the flavors will zing your tongue like drinking a glass of orange juice. This will help you sense the difference between tannins and acids in a red wine.
You know, I should really apologize to you. All this testing to discern the difference between tannins and acidity means you’re gonna have to go out and buy wine. And drink it. Lots of it.
Sorry about that.
Wondering if hydrolyzable tannins can be found in the stems of grapes? So am I. The research I’ve seen so far refers to the skins, seeds and stems as condensed tannins, but I have to wonder if the stems might contain hydrolyzable tannins as well since other fibrious materials such as bark or wood contain hydrolyzable tannins. f you find any information on this, please email me: firstname.lastname@example.org.
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