Wine is filled with aromas for you to interpret. That interpretation happens somewhere between your nose, your brain, and your olfactory system. You use this triangle to detect and recognize aromas in wine. But it’s this same system that allows you to detect flaws in wine. The rub is that you have to experience a wine fault before you really know it forever, and even then, the faults could be slight. Wine is a living thing that can sometimes throw us for a loop. Let’s start with aromas.
Even before the grape is crushed at harvest, there are little gems of aromas living in the sugars of the grapes waiting to be released through fermentation in the form of flavor precursors. Those pre-fermented aromas are known as the wine’s primary aromas — the berry, cherry, and tropical notes. After the wine is made and put into oak, there are natural compounds waiting in the grain of the oak that interact with the juice, adding to its flavor profile. The most well-known is vanillin, which adds the vanilla smell, but there are others with wacky names like guaiacol, which imparts smoky bacon and spice aromas; furfural, which adds butterscotch and almond notes; eugenol, which gives a slight clove smell to a wine; and syringol for a hint of roasted coffee. These are called secondary aromas or aromas brought about by oak influence.
As weird as it sounds, once the wine is bottled, it continues to evolve in a reductive state. Wine is always fining itself and reducing itself; this is how a wine ages. And in the absence of oxygen in a somewhat isolated state, all of these aromas or flavor compounds interact with each other, along with the structural elements of the wine like its tannins, acidity, and alcohol, precipitating or combing to gain weight and fall to the bottom of the bottle. When this happens, the flavor profile of the wine changes. All the primary and secondary aromas combine to create what is called tertiary aromas or the aromas brought about by aging. In the wine world this is when the “nose” of a wine becomes a bouquet. These are the more savory aromas, some say more sophisticated; they smells like mushroom, earth, or subtle spices like cardamom.
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To enjoy this plethora of aromas that are different from grape to grape and blend to blend, we use our olfactory senses to pick up what the wine wants us to experience. And often, these aromas are prominent enough that we know them right away. But everyone is unique in their olfactory department. See, all these aromas exist in certain amounts, and the higher the amount, the more likely it is that we experience them. This is called our sensory threshold, which is our ability to detect and recognize aromas. The ability to detect is based on how much of one aroma is in the wine and the recognition is your olfactory sense tapping into your sense memory. That’s all it is.
If you detect an aroma but just can’t place it, you have utilized one half of your sensory threshold. If the person next to you says asparagus and you smell the wine again and sure enough you smell asparagus, then your friend just jogged your sense memory and increased your threshold. I know this is not very romantic, but knowing that you are unique might give you more confidence in trying to detect and recognize aromas.
Not only is your sensory threshold unique to you; every aroma compound in wine has its own threshold. And they are all measured in very small amounts. I’m talking nanograms, micrograms, or parts per billion. Crazy, right? So if a wine has a certain primary aroma of cherry in its youth that measures high in the parts per billion, you are all over it when you stick your nose in that glass. You can detect and recognize it. But that same wine a few years down the road may have lost a bit of its cherry note due to aging, losing its PPB in the wine, and possibly making way for more tertiary aromas like mushroom to come to the forefront.
Aromas can also run wild, and we know this mostly from the vanillin compound. If a wine interacts with a flavor compound too much, that aroma can overwhelm the wine. Ever had a Chardonnay that has nothing but vanilla on the nose? That is aroma gone wild. But the popularity of vanilla allows us to tolerate the excess of such an aroma. If one of those other wacky-named compounds got out of hand, it may not be so enjoyable, like too much roasted coffee on the nose, or too much smokiness.
But just as all aromas are flavor compounds in micro amounts that your sensory threshold detects and recognizes, so are a wine’s faults. And that’s where it really gets interesting.
All wine faults are compounds overwhelming the other flavor compounds in the wine, masking all the wonderful aromas. If you have never experienced a wine fault, then of course you won’t know if a wine is corked or oxidized. But once you experience a wine fault and can detect and recognize it, from then on you will be able to asses whether wine has a fault.
The most well-known wine fault is cork taint. All over the world at any give time, three to five percent of wines are “corked” (it’s one of the reasons screw caps are used). Cork taint is the result of a wine being compromised by an organic compound with a very science-y name: 2,4,6 Trichloroanisole, otherwise know and TCA. The compound, often found in the porous nooks and crannies of a cork, drops into the wine and suppresses any fruit aromas. Only very tiny amounts are needed for this to happen; its detection threshold is 3-4 four nanograms per liter! So at that very small amount you would be able to detect that something isn’t right with the wine, though your recognition threshold could be less sensitive, especially if you haven’t experienced it before. TCA masks wine aromas with an all-encompassing wet cardboard or wet newspaper smell. If a wine has TCA but is below that 3-4 ng/l amount you may not even detect it and all is well.
Speaking of cork, remember how I said that wine is always in a reductive state? Well, the endgame for wine is when oxygen has had its way with it and turns a wine to vinegar. Sometimes a wine sees too much oxygen before you open the bottle because the cork is messed up or the wine saw too much O2 before it was bottled. Oxygen helps aerate a wine, expediting the reduction process and giving us all those amazing aromas. Oxygen also aids in aging a wine in small amounts. But if a wine has seen too much it can produce a compound called ethyl acetate, which is is a main ingredient in vinegar.
Brettanomyces is a yeast cell in the same family as the primary yeast used for fermentation, saccharomyces cerevisiae. But Brett, as it is called in the industry, is the black sheep in the family. Where saccharomyces cerevisiae converts sugar to ethanol or alcohol as a by-product along with carbon dioxide, Brett produces two by-products that, in very low levels of below 140 parts per billion, can give a wine some added complexity similar to what oak does, imparting smoky, leathery notes. But when it gets above 600 PPB, those subtle complex notes turn to medicinal-Band-Aid-and-mouse-pelt smell. And that is nasty.
If you ever open a bottle and it’s corked, go get your money back. Or, buy another bottle of the same wine and raise your sensory threshold!