When people think about where a wine’s structure comes from, they usually focus on the grape skins or oak barrels. But the truth is that grape seeds are often a significant force in shaping a wine’s mouthfeel. Grignolino from Piedmont is the perfect case study. Its name comes from grignolè, a word from Piemontese dialect for seeds or pips, and the grape has more than the typical wine grape - generally 4-7 vs. the typical 1 or 2. That extra dose of pips is what gives the wine its grippy, almost sticky tannins, that are surprisingly strong despite the wine's thin red appearance.
Seed tannins behave differently from skin tannins. Skins lend softer, rounder tannins and a broader flavor spectrum that can include fruit and floral compounds. Seeds, however, deliver a firmer, more bitter type of tannin. Researchers have shown that when grape berries have a higher proportion of seed mass, the resulting wines contain more tannin and present a sharper, more astringent mouthfeel. The key is how ripe those seeds are and how they’re handled in the cellar. If pressed too aggressively or macerated too long, seed tannins can overwhelm.
Studies on tannin evolution show that seed tannins come in both soluble and insoluble forms, and they change dramatically during ripening and vinification. Soluble tannins contribute bitterness while insoluble ones affect dryness and structure. Winemakers can manage these by adjusting maceration length or choosing gentler extraction methods, making the difference between a wine that feels harsh and one that has just the right grip.
In wines like Grignolino, winemakers lean into the tannin. Shorter maceration times and careful pressing balance the naturally high seed tannin levels so that the wines stay fresh, but still maintain their tannin. This gives them what some call a "crunchy" fruit experience in the mouth.
The influence of seeds isn’t unique to Grignolino. Winemakers around the world face the same decision: how much to allow seed tannins into the finished wine. Longer fermentations and heavier pressing almost always increase seed tannin extraction, which can raise bitterness and impact balance. In Bordeaux, Napa, or Barossa, managing seed maturity and extraction is a constant theme.
So the next time you sip a red that makes it feel like your tongue is sticking to the roof of your mouth, think about the seeds. In wines like Grignolino, seeds are not only part of the name, they are essential to the experience of the wine. Understanding their role gives you a deeper appreciation of how even the smallest part of a grape can change the entire experience.
Articles for reference:
https://pmc.ncbi.nlm.nih.gov/articles/PMC7382114/
https://pmc.ncbi.nlm.nih.gov/articles/PMC7079243/