Last but not least in the series on stink – odors in the fungi family.
First up is moldy-earthy smell (2-ethyl-fenchol and geosmine). The molecules responsible for making your wine smell like dirty beets are usually produced by microorganisms. The pungent smell is often caused by the lack of proper hygiene in winemaking equipment, especially vats or barrels. Empty barrels are tricky to keep clean and free of mold because the temperature and humidity inside are often just what these microorganisms are looking for. Once the pesky spores make their way into the pores of a wooden vessel, it’s almost impossible to remove them completely. Sure, some earthy qualities in a wine can be enjoyable, but to prevent a moldy-smelling mess, the winemaking team needs to keep it (those barrels) clean; prewash, clean, rinse, disinfect, re-rinse – you get the idea.
Speaking of moldy, another fault you’re probably more familiar with is cork taint. Since the 17th century, oak cork has been the bottle sealer of choice – it’s elastic, compressible and impermeable to liquids and gases. Its taste, similar to that of wood, also varies a bit depending on how it’s processed – stripping, seasoning, washing, etc. A slight taste of cork or pieces of cork floating in your wine glass should not be confused with cork taint. The former is considered pleasant by some and the latter is a problem with wine service. Here are some scenarios, though, where the wine’s corked:
1. A foul, putrid smell caused by yellow stains on cork harvested at the base of the trunk. Don’t worry, though, the chances of this one are about 1 in 100,000.
2. A taste of stagnant water caused by poor hygiene during the cork production process – the cork strips were not fully dried.
3. The smell of solvent or smoke caused by a narrow cork that created bottle leakage. Mold or bacteria might be present and visible on the cork when you open the bottle.
4. The smell and taste of mold and must (yum!) caused by 2,4,6, tricholoro-anisole or TCA – this potent compound is responsible for 90% of cork tainted wines. The formation of TCA happens when chlorine reacts with organic phenols (highly prevelant compounds in the winery; in grapes, in corks, in barrels, in wooden pallets and in structural wooden beams) to form chlorophenols. These in turn react with mold in the presence of moisture to form TCA. Our threshold for detection of TCA is very low (less than 1 billionth of a gram per liter), so a little taint goes a long way to spoiling your glass of wine.
What are your chances of running into a corked wine? I’ve seen figures ranging from 2-8% of all bottles on the market – yikes. We’ll tackle alternative packaging and closures another day.