In winemaking, concrete eggs are:
A. Used to minimize harsh tannin as in young red wines since concrete tends to absorb tannin molecules
B. Used as fermentation vessels and well-liked in certain circumstances since concrete does not contribute an oaky flavor and holds temperatures well
C. Used to contribute a wet rock flavor to wine which adds to the wine’s complexity
D. Used in the making of sweet wines because the thick concrete walls guard against oxidation during long fermentations
Concrete tanks have been popular in Europe for decades. Today, concrete is also made into large “eggs” used by many top estates worldwide for fermentation. Because concrete is slow to warm up and once warm, slow to cool, it holds fermentation temperatures well. Concrete, like oak, is slightly porous allowing minute amounts of oxygen to reach the wine and help it to evolve—all without the oak flavor that a new barrel would impart. And finally, the egg shape of a concrete egg fosters a natural rolling action during fermentation which helps the fermentation proceed evenly.