The Science Behind Why Your Wine Smells Like Farts

Wine can be a tricky thing to get into because it's surrounded by a culture of strong opinions expressed through carefully coded language that can seem elitist or outright nonsensical to outsiders. Your first wine tasting can feel like an alienating experience if you're surrounded by experts who understand exactly what's going on when you swirl your wine glass (it's introducing oxygen to the drink), and describe everything in terms such as "full-bodied" and "mature." 

Truthfully, a lot of the things sommeliers say are simply coded terms for very basic concepts. For example, Vinology Wine School explains that "full-bodied" refers to a wine that has a notably high level of alcohol and flavors, something they may also refer to by the even vaguer term, "big." Wines that are "mature" are simply those that have reached the point where they're ready to drink. With a quick peek at a glossary of wine terms, you can look fancy in a flash, but every now and then you'll open a bottle whose distinct aroma can only really be described as "farty."

If you happen upon a bottle that reeks of overcooked cabbage, you don't need to pretend that it's some special nuanced aroma that your nose is too unsophisticated to appreciate. It's actually a tricky issue facing winemakers, and it's called "reduction" (not to be confused with a wine reduction, which is a delicious type of sauce). According to The Real Review, reduction occurs when a wine contains excessive amounts of volatile sulfur compounds, known as VSCs. VSCs are a class of chemicals that include dimethyl sulfide, which smells like cabbage, and hydrogen sulfide, which smells like rotten eggs. Medical News Today reveals that hydrogen sulfide is also the source of the foul smell of flatulence, which explains why reduced wine does indeed smell like farts.

Wine Spectator explains that reduction is caused when a wine is deprived of air during the fermentation process. Oxygen is necessary to ensure that the molecules within the wine can polymerize (combine) and without the right amount of it, VSCs can develop. The opposite of reduction is called oxidation — overexposure to air — and according to Wine Spectator, it can take on unpleasant aromas. Therefore, winemakers have to be careful to ensure that their product is exposed to just the right amount of air, as tipping the scale too far in either direction can spoil the product.

Reduction in wine is not always a bad thing, as a certain degree of oxygen deprivation is required to protect against oxidation. For this reason, Wine Searcher explains that there is a distinction between "reductive," a term used to describe the common practice of making wine in oxygen-controlled environments, and "reduced," the presence of volatile compounds in one's wine. Some people actually like their wine to have a bit of a reduced aroma. However, if you dislike these traits, or you encounter a wine that has clearly been over-reduced, there are some ways to fix it.

Keeping in mind that reduction is caused by a lack of oxygen, you can sometimes reverse the effect by pouring the wine into a decanter, says Wine Shop at Home. The old swirl-your-glass trick can also help. According to Live Science, another way to eliminate reduction is to place a copper penny into the wine, which can convert some of the volatile compounds in the wine.