If you detected the familiar aroma of coconut in a young Merlot wine, you might surmise that it was derived from barrel aging and characterize it as a secondary aroma. Likewise, if you perceive dried-fruit aromas of figs or prunes, you might conclude that those tertiary aromas indicate the wine had considerable bottle age.

Yet the aromas of coconut and dried fruit that we typically associate with secondary and tertiary development can also be found in must and young wine. In a July 2023 study by Alexandre Pons, a research scientist at the University of Bordeaux and Seguin Moreau France, the compounds responsible for those aromas in must and young red wines were identified as furaneol and homofuraneol.

The concentration of these compounds as well as that of γ-nonalactone, which is reminiscent of coconut and cooked peach, depends on vintage conditions and the amount of sunlight grapes receive during ripening, with the highest levels of γ-nonalactone being found in Merlot and Cabernet Sauvignon.

When grapevines are stressed by heat or by Uncinula necator, a fungus that causes powdery mildew, the metabolism of the berry is affected such that during fermentation yeasts can produce large amounts of γ-nonalactone.

A demonstration of that connection can be seen in Merlot and Cabernet Sauvignon wines from the 2007 and 2010 vintages in Napa Valley, which yielded higher levels of γ-nonalactone in the wines due to heat spikes close to the harvests.

Winemakers have a particular interest in understanding the origin of coconut and dried-fruit aromas in must, as they can point to premature oxidation. Researchers at the University of Bordeaux have identified both another lactone, massoia lactone, which smells like coconut and dried figs, and (Z)-1,5-octadien-3-one, a fig-like aldehyde, that contribute cooked and dried-fruit aromas in red grape must.

In a previous column titled “The Trilema of Primary, Secondary and Tertiary Aromas,” for the August/ September 2017 issue of The SOMM Journal, I discussed the paradox of grape-derived compounds like 1, 1, 6, -trimethyl-1,2-dihydronaphthalene (TDN) being categorized as a tertiary aroma when TDN is also found in must and detectable in young wine.

According to research by Vicente Ferreira, head of the Laboratory of Aroma Analysis and Enology at the University of Zaragoza in Spain, tasting rubrics like the Wine & Spirit Education Trust’s Systematic Approach to Tasting and the tasting grid preferred by the Court of Master Sommeliers for codifying wine aromas were state of the art when developed, but recent advances have allowed researchers to expand the wine-aroma universe by linking the seven aroma-precursor systems in grapes to potential aromas.

Ferreira’s research pushes beyond the boundaries that have been the standards by which the wine industry has trained wine professionals for the past 50 years. Even though the grape genome was decoded more than ten years ago, we still don’t have an understanding of all the grape metabolites that ultimately contribute to the aromas of wine.