1. What Tannins Are
Tannins are a family of plant polyphenols found in grape skins, seeds and stems, and in oak. In wine, they contribute to structure and the drying sensation known as astringency. They are part of the wine's character.
2. Seed and Skin Tannins
Seed tannins are generally described as more bitter and astringent than skin tannins when the grapes are young. Skin tannins tend to be softer and more fruit-related. The balance depends on ripeness, extraction and the winemaking method, so the two types are managed together rather than separately.
Tannin sources and their typical roles (qualitative)
| Tannin source | Typical character when young | Role in ageing |
|---|---|---|
| Seeds | Firmer, more bitter, drying | Polymerize over time into larger molecules |
| Skins | Softer, fruit-linked | Contribute colour stability and structure |
| Oak | Adds spice and structure | Can add tannin and support longer ageing |
3. Polymerization During Ageing
As wine ages, tannin molecules link together to form larger polymers. Larger molecules interact differently with saliva and the palate, so the perception of astringency often softens. Oxygen, which enters slowly through the barrel or closure, and time both influence how far this process goes.
4. Practical Management
Winemakers manage tannin through picking time, the length of skin contact, pressing and the choice of oak. Gentle handling of seeds, avoiding excessive crushing, and monitoring the tannin profile through the ferment help keep the final wine balanced.
5. Tasting With Attention
When tasting a wine for tannin structure, pay attention to texture, length and the way the astringency changes across the palate. Tannin perception varies between people, so comparisons are most useful when made side by side.
6. Maceration and Gentle Extraction
Maceration is the period when the juice stays in contact with the skins and, for red wine, the seeds. Longer maceration extracts more tannin. Gentle extraction, such as cold soaks and gentle punch-downs, aims to draw out softer, more fruit-related tannins and avoid harsh seed tannins. The balance between the two is a key decision in red winemaking.
7. Seed Versus Skin Phenolic Maturity
Seeds ripen more slowly than skins. If grapes are picked before the seeds are mature, the seed tannins can taste green and harsh. Many winemakers check seed ripeness by tasting the seeds before deciding on the picking date, because the skin can look ripe while the seeds are not.