The Chemistry of Wine

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You don’t need to be a connoisseur to know that the flavors and smells associated with wine exist across a vast spectrum. But what exactly is going on to create these distinctive aromas? Read our article on the chemistry of wine to find out.

Wines offer us a variety of aroma and flavors, some flying confidently from the bottle with the pop of the cork, others developing slowly and delicately as the wine breathes, or when it hits our palette. Wine bouquets are described variously as buttery, floral, smoky, or chocolatey. They may be bestowed with labels claiming flavor notes as diverse as berries, plums, pepper, spice, nuts, cream, vanilla, oak, or grass. How can this be for a liquid made entirely from grapes? Of course, it all comes down to chemistry and the release of volatile organic compounds.

Every glass of wine has unique nuances of taste and smell that come from complex chemistry. Any bottle is 98% water and ethanol, no matter its provenance; but it’s the remaining 2% that makes the difference. The grape varietal itself is important, and there are more than 10,000 varieties used in wine making, all producing different tastes and smells, and each host to different types of yeast that play their part in fermentation. But flavor can also be impacted by external factors, such as processing and storage. For example, the type of wood used to make the barrels that the wine is aged in can add extra tannins to the mix, bringing bitterness and astringency. Climate too can have an effect, since fruit sugars develop more slowly at colder temperatures, meaning that vineyards in cooler climates make subtle, lower alcohol wines, whereas hotter locations results in stronger, more robust products. Terroir is an additional concept to take into account when considering the diverse and complex chemistry of wine. Terroir describes the character brought to the wine by the unique physical and biological growing environment that influences distinctive characteristics in the grape – from the organic and geological makeup of the soil to the particular layout of the vines and the degree of sun exposure and irrigation. There are over 60 trace elements found in wine that come from the soil – such as sodium and potassium cations that may give a salty taste. Terroir is a uniquely individual signature that would be impossible to copy, and is responsible for sensory diversity even within wines of the same variety.

Each of these elements contributes to the chemical fingerprint of the wine, and each tonal aroma can be attributed to a certain volatile molecule. Research has shown that the buttery flavors of chardonnay come from diacetyl, while the peppery notes in deep red wines like Shiraz are caused by methoxypyrazines or sesquiterpene α-ylangene. Green aromas come from 3-isobutyl-2-methoxypyrazine and C6 compounds, while tropical or grapefruit notes arise from 3-mercaptohexanol, and mint or cool eucalyptus flavors from 1,8-cineole.

Advances in wine chemistry help growers to understand their product and can give pointers on how to develop new flavor combinations. Wine making is a precision science, and with a vast number of choices to make over cultivation, process and storage, there could be many new aromas and flavors of wine yet to evolve – and for us to try. Bottoms up!

1. Herderich M et al. Terroir Effects on Grape and Wine Aroma Compounds. In: Advances in Wine Research; Ebeler et al. ACS Symposium Series. American Chemical Society: Washington, DC, 2015.
2. The chemistry of wine. Available at: http://www.acs.org/content/acs/en/pressroom/newsreleases/2015/july/chemistry-of-wine-video.html.
3. Ebeler S. Analysis of Grape and Wine Composition and Flavor. Available at: http://presentations.acs.org/common/media-player.aspx/Fall2014/AGFD/AGFD/PODAGFD5.