Geosmin

Geosmin refers to a molecule responsible for an earthy, musty fault in wine, produced by soil bacteria and fungi such as actinomycetes. Extremely potent, it stays perceptible from roughly twenty-five nanograms per litre, evoking beetroot, damp soil and mushroom. Frequently linked to rot-affected grapes or contaminated water, it masks the fruit and proves difficult to remove once established, since remedial treatments rarely restore the wine's original aromatic profile.