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Esters in Wine: The Science behind Wine Aromas

I used to play this game with my aunt whenever we enjoyed wine with dinner: without looking at the wines back label, we’d try to pick out the notes and aromas of the wine (all the while looking and feeling as pretentious as ever, of course), and compare it to the notes the label depicted. My aunt was and is still the undisputed champion at discerning the different aromas within the bouquet, whether it be cinnamon, peach or vanilla, but it did get me thinking: wine is made out of grapes, yet somehow I can smell and taste raspberries in my wine? What gives?

The answer to that, quite simply, is due to the presence of little chemical soldiers called esters.

We’ve introduced and explained what esters are, and the role they play in developing the aroma profiles in wine in our article on Wine Ageing, but here’s a one-stop summary of what esters are:

What are Esters?

Esters are organic acids that occur naturally during the fermentation process in wine. When grapes ferment, yeasts consume the natural sugars produced when the grapes ripen, and the byproduct of this reaction is Carbon Dioxide, Alcohol and over 200 aromatic esters. Esters are responsible for the different aromas that we experience in everyday life, from pineapples (Ethyl Butanoate) to that Christmas tree smell that we all love (Bornyl Acetate).

Generally, in wine, esters are commonly attributed to imparting a ‘fruity’ smell to wines. Each grape variety has a unique chemical make up with varying amounts of these organic esters, that upon processing will give rise to a host of aromas. Coupled with the esters from oak barrels and wine maturation, we have a whole portfolio of wine esters that contribute to its overall aroma profile.

In younger wines, primary aromas of fruits are dominant: these typically include notes of red berries, cherry, blackberries and blueberries in red wines. In white wines, the aromas most expressed are apples, pineapples, citrus and other tropical fruits. As the wine ages, secondary and tertiary aromas develop, which include tobacco, smoke, truffle and earth. These qualities are typically sought after, as only high-quality wines are capable of ageing to develop this bouquet.

However, not all esters impart a pleasant smell to wine. The ester that is responsible for the unpleasant smell associated with a wet dog is 2,4,6-Trichloroanisole, which is a surefire indicator if the wine has been exposed to the bacteria responsible for cork taint; otherwise referred to the wine being corked.

It usually takes time and experience to develop your palate so you’re able to identify the various aromas in your glass, however, all these smells and tastes have been usefully compiled into an aroma wheel to help wine novices better understand and identify the tastes and aromas in wines.

Wine aromas wheel

With that being said, to generalize all aromas in wine to just esters would be to paint with a broad, broad brush. Wine, as an organic substance, is an immensely complex matrix of chemical compounds that includes esters, aldehydes, pyrazines, sulphites and other substances, which in symbiosis with one another, give rise to the most unique and multifaceted development of aroma and flavour that science just has not fully understood yet.

So, while we’re still waiting for the science to catch up, you may just impress your friends with your knowledge of the different notes and aromas of your wine from using the above aroma wheel!

The Author

Kaylyn Chandran