Hello there! I'm Dr. Vinifera, but you can call me Vinny. Ask me your toughest wine questions, from the fine points of etiquette to the science of winemaking. And don't worry, I'm no wine snob—you can also ask me those "dumb questions" you're too embarrased to ask your wine geek friends! I hope you find my answers educational, empowering and even amusing. And don't forget to check out my most asked questions and my full archives for all my Q&A classics.
Dear Dr. Vinny,
Considering the fact that tannins come from natural sources such as seeds, grape skins and wood, can an aging, deteriorating cork affect the balance of a wine?
—Shay, New York
What a great question. Cork is made from tree bark and, as you noted, tannins are present in wood. So yes, there are tannins in cork, as well as other phenolics you might expect to be present in a piece of tree bark.
But will cork components migrate into a wine after bottling and affect a wine? There has been some research into this area and it appears that yes, phenolic compounds and tannins can be extracted into wine (though the study involved grinding up cork into a powder and occasionally agitating the solution—not exactly the circumstances found in most wine bottles).
Keep in mind that the surface area of the cork is pretty small, and a quality cork (and quality storage conditions) should keep a cork intact. That said, some transfer of tannins and phenolics are part of the equation of aging wine under cork.