Traditional bottle cap from the outer bark of cork oak growing in the Mediterranean. It lets the atmospheric oxygen get into the bottle, which then ripens the "breathing" wine. But the maturation of a wine includes, as with any living product, the development to its climax and the subsequent "degradation of the personality," which makes the "experience of wine" so fascinating. On the other hand, cork oak plantations in Portugal (80% of cork), Spain and France are almost exhausted.
The mouldy, bitter taste of a cork error can immediately be detected, when the bottle is opened. Neither the winemaker nor the restaurateur is at fault for such a condition. It can be a single bottle from an otherwise impeccable assortment affected. This is the (often unknown) main reason why the waiter in the restaurant pours the guest a little bit, in order to taste it. Cork taste always entitles to the return of a wine. For some years, the use of cork has been decreasing in favor of screwcaps.