Musty aroma in wine due to Cork Taint

Musty aromas and corked wine

The major compound responsible for musty taints from cork is 2,4,6-trichloroanisole (TCA). This is formed in cork bark by the chemical combination of phenolic compounds with chlorine.

(There are other compounds that can cause musty taints, but TCA is largely responsible. )

Smelling the cork when removed from the bottle or sample tasting of wine can assure you that the wine is not 'corked'. 

Sampling wine from a screw cap, is like sampling your beer before enjoying it, there should be no cork taint in a screw cap wine.

"The compounds in TCA are present as a result of the breakdown of lignin, which is the hard substance naturally occurring in tree bark. The chlorine comes from the environment It is widely accepted that the major source of environmental chlorine in cork oak forests are organochlorine insecticides that were widely used from the 1950 to the 1980. Even though they are no longer used, chlorine residues are still present in the soil at the base of the trees and will remain there for some time."

We are extremely sensitive to TCA, but apparently TCA itself, at the levels found in tainted wine, is harmless. 

Some people are extremely sensitive and others can't smell it at all, they are anosmic to TCA. (article extract from Flawless, Jamie Goode) 

Alternative closures are used, but we believe in the traditional maturation of a natural cork closure. Smelling the cork after I open the wine has become second nature.