Written by: Tim Edison

Updated: September 27, 2023

What Are Wine Tannins? [Simple & Detailed Explanation]

red wine being poured into a glass

Have you ever tasted pomegranate and experienced that drying sensation in your mouth? 

Those are tannins at work.

You get a similar effect from red wines that are high in tannins like those made with the Nebbiolo grape. Barolo is one such example.

Tannins play a crucial role in our appreciation of wine and also the preservation of it.

But what exactly are tannins in wine?

Impress your friends over your next glass of wine with our explanation below.

What are Wine Tannins?

A general search of the term ‘tannins’ will lead you to discover that woody plants most commonly make tannins, but that they can also be found in everything from ferns to persimmons. 

Tannins are naturally astringent (slightly acidic or bitter), and this astringency is a deterrent to virtually all plant eaters, including insects, birds, reptiles and humans. 

But how can this have anything to do with wine? At least anything good anyway!

In the right amounts and concentrations, tannins can lend several qualities and complexities to wine.

Obviously, one can enjoy all of the benefits that wine has to offer without knowing the details of what goes in to making a fine wine. 

I find that there is added enjoyment when one becomes more knowledgeable about the wine they are drinking and the process it takes to go from grape on the vine to wine in the glass. 

To give a very simple, basic and easy to understand definition of what wine tannins are, consider the following: 

Tannins are naturally occurring compounds that exist inside the skin, seeds and stems of grapes.  

Scientists give a scientific name to these compounds – polyphenols.

pouring red wine in a glass

Understanding Polyphenols

As we will see, these polyphenols are a group of compounds that are extremely important in the wine making process, and this importance increases even more so in red wines. 

It's these polyphenols that are responsible for many of the health benefits you see attributed to red wine.

The name “Polyphenol” comes from the basic building block of this class of chemicals, which is known and referred to as the phenol group. 

Without getting into too technical of a description, these chemicals are highly reactive, meaning that they like to stick to other things and associate spontaneously with a wide range of different compounds. 

So what do polyphenols do, and what is their effect? 

Well, these compounds are released from the skins, seeds and stems of the grapes as they soak in the grape juice as soon as the grapes have been pressed. 

As the polyphenols are released, they can give certain types of wine a particular astringent quality. It can also be described as a drying mouth sensation.

Obviously, certain wines are considered “dry” wines, and it is this type of wine that is typically high in tannins. 

Bunch of grapes isolated on white background

How are Tannins Expressed in Wine?

But, what makes a certain wine have strong or weak tannic qualities?

Was it the type of grape, the quality of the grape, the region the grape was grown in, or perhaps something else? 

Well, after researching a little further, I discovered that it is the length of time that the aforementioned skins, seeds and stems of the grapes actually sit or bathe in the grape juice after the grapes are pressed. 

If the skins, seeds and stems of the grapes are allowed to soak in the juice for a longer period of time, then this will lead to the creation of a wine that will contain more tannins, and hence a drier taste

Conversely, if the soaking time is relatively short, this will create a wine with little or no tannic characteristics. 

This helps explain why many red wines have a much stronger tannic quality than white wines, which often taste sweeter and less bitter than the red wines do. 

When winemakers are in the process of crafting a red wine, part of the process that allows the wine to become a darker and richer red in color, is letting the grape skins soak in the grape juice for a longer period of time. 

In doing this, more tannins are released into the juice. The longer the skins soak, the darker the color of the wine. 

Another byproduct of this process is the wine will take on a much more complex taste than if less tannin were released. 

The greater the amount of tannins in a wine, the greater the bitterness and astringency in the wine’s finish can be. This increase in astringency is often what makes many people who are relatively new to tasting and sampling wines avoid red wines.  

The tannins can create sensations in a wine drinker’s mouth that can either be silky and velvety to very dry and bitter.

Tannins can also come from another source besides the grape itself.  As wine is being aged in oak barrels, tannins from the oak itself can leach into the wine. 

If wine is being aged in newer oak barrels, the level of tannins will be higher, and these oak barrels can add noticeable mouthfeel and flavor to the wine.

red wine being poured into a glass

The Benefits of Tannins

So, if an increased amount of tannin can give a wine a deeper, richer color, and a more robust and complex taste, are there any other benefits to these tannins? 

Of course there are! 

The tannins also help protect a wine from the aging process, since they are a natural antioxidant. 

When you start figuring these tannins out, you can quickly start to see why some of your best red wines have the most complex flavoring, deepest coloring, and actually get better as they age. 

As I am discovering all of these facts, I am now starting to tell myself that I need to start tasting some of these red wines, so that I can appreciate all of the qualities that the tannins bring to the wine. 

Some of the red wines that have the highest tannin levels include Petite Sirah, Montepulciano, Monastrell, Nebbiolo, Petite Verdot, and one of the most popular wines, Cabernet Sauvignon.

Now that we know what some of the qualities and characteristics tannins bring to different types of wines, particularly red wines are, it begs the question, are there any other benefits or risks to be had from drinking wines that contain higher levels of tannins? 

It is possible as some scientific evidence suggests, that wines high in tannins can lead to lowered blood pressure, improved immune response (thank those antioxidants), and a greater balance in blood sugar. You can read all about these studies and the potential health benefits of wine in our guide.

It can now be seen from all of this that one of the keys to successful red winemaking is the effective management of tannins. 

The first place a winemaker can begin this process is obviously as the grapes are being grown in the vineyard, as the grapes, seeds and stems can all contribute to significant levels of polyphenols in the wine. 

As the grapes mature on the vines, they have been traditionally harvested on the basis of sugar levels, or when they appeared to reach the perfect ripeness visually.  

As wine production now has a greater focus on tannin management, grapes are often harvested when they reach a so-called “phenolic” maturity.  

If grapes are harvested when they have yet to reach maturity, the quality of the wine produced will be negatively affected, primarily due to the presence of unripe green tannins.  

Thus it can be seen why waiting to harvest until this “phenolic” maturity has been reached.

Once the decision to harvest the grapes has been made, and the harvested grapes make their way to the winery, winemakers have the task of deciding the best way to macerate the grapes so as to achieve the best level of tannin extraction. 

This can be done through the alteration of the temperature that fermentation takes place at, the type of container used for fermentation, such as small or large volume. 

Constant experimentation and research is being undertaken in an attempt to fully understand the best and most efficient ways to achieve a perfect balance in the tannin levels of red wines.

Final Thoughts

As the wine growing and wine making processes continue to evolve and invoke much more of a scientific tone, we can be sure that we will continue to learn more about these tannins, and the role they play in the crafting of fine wines. 

Did you know how important tannins were to the wine you like to enjoy now and again?

Perhaps the next time you pour a glass of your favorite, you will give at least a thought to what went into the process that produced your wine.

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About the Author Tim Edison

Tim started Wine Turtle way back in 2015.
These days he contributes to Wine Turtle (and other renowned wine publications) while continuing his wine education.
Tim's wine of the month is the Coates & Seely Reserve Brut NV (from Hampshire, England).

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