Want to know the best time to drink a bottle of fine wine? Give it a sniff

Why are the aromas of well-aged wines so appealing? Normally, we favour fresh smells: newly baked bread, fresh linen. Yet when it comes to fine wine we like the mature smell of graceful degradation. What are the older wine aromas that we pick up on and why are they so prized?

As wines age their aromas develop greater complexity, readily discernible on the nose. These merit a separate term in professional wine circles: bouquet. Many people use the terms aroma and bouquet interchangeably, but Emile Peynaud, the father of modern oenology, reserved the term bouquet for the distinctive harmony of odours that is only achieved with time.

The primary aromas are those due to the characteristics of the grape variety, like the bell pepper of Cabernet Sauvignon. Secondary aromas are fermentation products, like the notes of popcorn or butterscotch in Chardonnays that have undergone a long malolactic fermentation. The emergence of tertiary aromas, like honey in whites or truffle and undergrowth in reds marks the end of a wine’s youth.

A mature wine offers pleasure and sophistication on the nose. Textures and tastes soften but a wine’s aromatic profile develops with age, producing, in the case of claret, that beguiling smell of old libraries and furniture polish. Young wines can never have these characteristics. That’s because the maturing of a wine transforms it, producing volatile compounds that wine chemists are just beginning to understand.

A new study from the lab of Gilles de Revel and Stéphanie Marchand at the University of Bordeaux has identified several of these compounds in fine aged claret. The harmonious bouquet of these wines often reveals typical and highly desirable notes of undergrowth, truffle and, surprisingly, fresh fruit notes of cassis, while poorly aged wines reveal tell-tale off-notes of prune and fig.

A key question for the quality of aged fine wine is when to drink it. Most achieve a plateau for several years before they begin their gradual decline. The condition of these wines will depend on the preponderance of particular volatile compounds; the ones we favour in the end is a personal or cultural matter. The British think the French drink their claret far too young—eight to 12 years after the vintage; the French think the British drink their wines far too old—after 20 years or more.

The analytic chemists are beginning to identify, among wine’s active compounds, the precursors of the volatiles that will produce the intoxicating bouquet of a decently-aged red Bordeaux. So, in future, it should be possible to tell with even greater precision if any bottle is worth keeping.

Similarly, another study in Dijon by Jennifer Langlois and colleagues examined the basis on which wine professionals decide if something is a vin de garde (a wine worth keeping). Bottles of the wines used are being carefully stored to open up years from now so we can analyse how they fared from a sensory and chemical standpoint. Did the wine professionals pick out true vins de garde? Time will tell.