Issue link: http://digital.copcomm.com/i/935769
{ SOMMjournal.com } 83 WHO'S AT FAULT? For many reviewers and wine judges, cork taint can be a scapegoat for a host of problems hov- ering elusively below the sensory threshold. "We see reductive and oxidative faults occurring at a much higher incidence than brettanomyces and 2,4,6-Trichloroanisole [TCA]," Lopes said during his presentation. In tackling the dynamic winemakers face between working anaerobically or reductively and aerobically, Lopes dispels the myth that the former can successfully "freeze the wine in time." Reactions can occur in the absence of oxygen, with the most notable being the formation of smelly sulfur compounds. Lopes furthered this point in his research by using an unadulterated sample as a control along with four doctored samples of Chilean Sauvignon Blanc. He selected this control wine for its thiols—aroma compounds with tropical-fruit and citrus flavors. "Sauvignon Blanc has distinct markers; it's very rich in sulfur-like compounds, including methoxypyrazines, which have grassy, vegetal notes and can be an indication of reduction," he explained. Oxidation in wine can occur via two pathways—alcohol or phenols. Either way, it's relatively easy to identify and can be attributed to a host of factors not related to cork. Browning in white or red wines is a dead giveaway of oxidation. Too little nitrogen in the vineyard, heavy- handed pressing in the winery, and bottling at low temperatures can all contribute to oxidation. The result of alcoholic oxidation is acetaldehyde, a sherried or aldehydic character that's cher - ished in oxidative-style fortified wines like Sherry but detracts from the quality of still table wines. This results in a bruised-apple character on a palate that is flattened, dry, diluted, and bitter. Reduction, on the other hand, doesn't affect color ; it's detected by aromas and can cause astringent, buttery, or metallic flavors that originate from natural or added sulfur compounds. This family of volatile sulfur compounds can have a positive or negative impact on wine. Desir - able compounds are formed by long-chain thiols, while the undesirable compounds that mask primary-fruit character and produce reductive off-flavors are short-chain thiols. Because yeast produces sulfur dioxide during fermentation and there are other naturally-oc - curring sources of sulfites in wine, winemakers want to reduce the potential formation of sulfur compounds. Lopes showed us three reductive faults: hydrogen sulfide, which has the smell of rotten eggs; ethanethiol, a compound that's reminiscent of garlic, natural gas, and pesticides; and one of the simplest sulfur compounds, methanethiol, which reeks of dirty drains and cabbage. For the latter, prevention is the only real "cure." Through these faults, Lopes demonstrated the vital role played by the oxygen transmission rate (OTR) in wines and the effect that particular closures have on the potential for reduc - tion to emerge after bottling. In his studies, screwcaps were most effective at increasing levels of both good and undesirable volatile sulfur compounds (VSC); natural cork, meanwhile, fared better in showing lower levels of bad compounds and had an equal impact on certain types of good VSC. Dr. Paulo Lopes, Research and Development Manager at Amorim Cork.