What are wine tannins and where do they come from?
Wine tannins are natural compounds responsible for much of a wine’s structure, texture, and aging potential, especially in red wines. They’re often described as a dry or grippy sensation, but understanding what tannins are and where they come from helps you read a wine more clearly, choose more confidently, and make sense of how it can evolve over time.
In wine, tannins mainly come from two sources: the grape and oak (barrel aging). Each source tends to shape the final style in a slightly different way.
Quick summary
- Wine tannins come mainly from the grape, and in oaked wines also from oak.
- In the grape, tannins are concentrated in skins, seeds, and stems.
- Knowing the source helps explain texture (silky vs firm vs more herbal/green).
Grape tannins: skins, seeds, and stems
The grape is wine’s main natural source of tannins. These tannins are part of the broader family of polyphenols, naturally present in different parts of the berry and cluster.
| Grape part | What it tends to contribute | How it’s often perceived (in general) |
|---|---|---|
| Skins | Structure and volume | Finer astringency when ripe |
| Seeds | More concentrated tannin | More bitter and drying if dominant |
| Stems | Powerful, vegetal tannin | A more marked, “green” grip if not integrated |
Tannins from grape skins
The skin is usually the most important—and most desirable—source of tannins in quality red wines.
- Extracted during maceration, when the juice is in contact with skins.
- Contributes structure and volume, with a generally finer, more balanced grip.
- Often feels more silky when the grapes are well ripened.
How much (and how refined) skin tannin you get depends on factors such as:
- Grape variety
- Ripeness
- Length and technique of maceration
That’s why varieties like Nebbiolo, Cabernet Sauvignon, Syrah, or Tannat are widely known for naturally tannic profiles.
Tannins from seeds
Seeds contain more concentrated tannins that can feel more aggressive.
- Released when seeds are crushed, or when they stay in contact for too long.
- Can bring a more bitter and drying impression.
- Often less desirable if they dominate, because they can harden the overall feel of the wine.
Modern winemaking typically manages extraction carefully to avoid too much seed tannin—especially when grapes aren’t perfectly ripe.
Tannins from stems
Stems (the woody part of the cluster) contain very potent, vegetal tannins.
- Their impact depends on whether the wine is destemmed.
- They can add herbal notes and a firmer grip.
- Used intentionally only in certain specific styles.
In most wines, stems are removed to avoid overly “green” or excessively drying sensations.
Oak tannins: the influence of barrel aging
Beyond the grape, tannins can also come from oak, especially when a wine is aged in barrel.
How barrels contribute tannins
During aging, wine extracts from the wood:
- Tannins
- Aromatic compounds
- Structural compounds
These oak-derived tannins can:
- Increase perceived structure
- Support stability and aging
- Feel more sweet-toned and enveloping when well integrated
The impact depends on factors like:
- Oak type (French, American, etc.)
- Toast level
- Time in barrel
- Barrel size
Practical differences between grape tannins and oak tannins
They’re both tannins, but their origin often creates a noticeably different feel.
| Quick comparison | Grape tannins | Oak tannins |
|---|---|---|
| Source | Fruit (skins/seeds/stems) | Oak (barrel) |
| Typical contribution | Varietal character and core structure | Complexity, roundness, and support |
| Typical sensation | More direct grip/astringency | Often softer when integrated |
Grape tannins
- Come from the fruit
- Help define varietal character
- Often read more directly as astringency
- Key for natural aging potential
Oak tannins
- Come from oak
- Add complexity and roundness
- Often feel softer in terms of grip
- Reinforce the structure already present in the wine
A well-balanced wine often combines ripe grape tannins with measured oak aging, without either dominating.
Why understanding tannin origin matters
Knowing where tannins come from helps you:
- Anticipate how a wine may feel on the palate
- Understand whether it might need time to round out
- Choose styles that match your preferences
- Better assess quality and style
Far from being a flaw, well-managed tannins are one of the pillars that make a wine feel structured, food-friendly, and capable of evolving with time.
In the next articles of this guide, we’ll go deeper into how tannins feel, how they change with aging, and which wine styles tend to be more tannic, so you can interpret each glass with more confidence.