Balance and Complexity: How Oxygen and Aromatic Interactions Impact Wine

“Terrific wine. So complex…”

Complexity is at the heart of great wine–it’s truly fascinating when everything seems to fit together like pieces of an intricate puzzle and every sip seems to deliver something new.

So many elements come together, so many things change and combine as grapes turn into wine, and as wine evolves, it easily becomes the subject of endless arguments and discovery. Grapes, climate, soil, viticulture, and oenological practices–all these factors influence the outcome and the expression of the wine. Add to that a layer of perceptions, which differ from person to person and from one context to the next, and you get an almost infinite range of possibilities.

At a very basic level, however, this complexity in perceptions is the result of the complexity in the chemical composition of the wine itself. A wide range of aromatic components can be present in the wine, and they come in many categories: thiols, fruity esters, fatty acids, lactones, terpenes, methoxypyrazines, volatile phenols, and others. Within these families are dozens upon dozens of different components, which all have their signatures and particular aromas.

The emergence of a complex bouquet has a lot to do with the presence of many different components in the wine itself, of course, but it also is shaped by the way these compounds interact. Certain compounds act as boosters for others, making them more easily perceptible.

Building blocks

wine-swirl-For example, we’ve seen on this blog that dimethyl sulfide (DMS) in low doses brings out fruity aromas in red wines, which can contribute significantly to persistence of fruity notes in older wines and thus, to the complexity of the aging bouquet. It can also provide delicious notes of truffles. Similar things happen with acetaldehyde, which brings out fruity aromas when present in low concentrations (around 10 to 20 parts per million). Both compounds, on their own, are better known for the unpleasant smells they generate, like rotting cabbage for DMS or browned apples for acetaldehyde. So, it’s really the interaction that turns things around and makes the total greater than the sum of the parts.

Another study published in 2013 found that when certain esters (ethyl-3-hydroxybutanoate and 2-methylpropyl acetate, chiefly) were present in “aromatic reconstructions” (model solutions reproducing concentrations of various compounds found in wine), they made aromas like fresh fruit and blackberry more easily perceptible in sensory tests, while their absence attenuated the intensity of the same aromas. Aromatic compounds don’t just cohabitate, they also function as building blocks for the overall expression of a wine, with some supporting others–and sometimes, hindering others.

That blocking or hindering effect of certain compounds on the aromatic expression of a wine was also pointed out in a South African study. In particular, the study highlighted how a compound called methional can cover up the thiols that define Sauvignon Blanc, so that instead of getting passionfruit and grapefruit, you wind up with cooked beans and cooked potatoes. Again, the aromatic compounds that provide the pleasant aromas are still present in the wine, but they become difficult to detect because the other compounds cover them up.

A balancing act

Interestingly, methional appears in the wine because of excessive oxidation, showcasing how important it is to manage oxygen at all stages of winemaking. Steering the wine carefully, in terms of how much or how little oxygen they receive, is key to making sure all those compounds present in the wines actually show up on the nose.

Wines that suffer from excessive oxygen ingress or highly reductive conditions (something that can mean different things with different wines) will inevitably see compounds emerge in a way that is likely to mask the complexity of the wine and reduce enjoyment–if nothing else. While acetaldehyde, on the oxidative side, starts to play a negative role when its concentrations rise, the same thing happens on the reductive side when sulfur compounds build up in wines with things like H2S and mercaptans creating smoky, stinky and sometimes even rotten aromas that mask the fruity character and other more pleasant aromas.

Achieving complexity in wine requires good grapes with concentration and maturity, to start with, but the complex array of aromatic compounds found in the grapes or generated by fermentation will only express themselves fully if the vinification allows them to come out unhindered.

Complexity requires balance, and that balance must appear in the winemaking, so that balance can appear in the bouquet as well.

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About the Author

Rémy Charest is a Quebec City-based journalist, writer, and translator. He has been writing about wine and food since 1997 in various Canadian and American print and online publications, includijng Le Devoir, Le Soleil, Coup de Pouce, EnRoute, Palate Press, Punch Drink, WineAlign and Châtelaine, and has been a regular radio columnist for Montreal's CJAD and CBC/Radio-Canada. He is additionally a wine judge for national and international wine competitions, notably the National Wine Awards of Canada and the World Wine Awards of Canada organized by WineAlign.

Rémy Charest Photo Credit: Jason Dziver

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