Biology of bouquet: Why do some wines smell like latex, grass or limes?
How does your nose know the difference? (photo courtesy of Stock.Xchng)
I will state for the record that I am not a wine connoisseur, even though I write occasional posts about wine and food pairings. My interest in wine is superficial and purely amateur.
However, I enjoy reading wine reviews and watching some of the wine commentators on YouTube, such as Gary Vaynerchuk, of tv.winelibrary.com.
Why do I like reading these reviews? Well, the wine critics unending search to find more superlative as well as derisive food-based adjectives to describe the taste of the particular vintage of grape wine can be quite entertaining to anyone who loves the English language and has training in wielding the written word.
Watch Vaynerchuk’s Sept. 24, 2008, review of three sauvignon blanc and semillon varietals, starting at about the 8:00 mark. Listen as he describes a Napa Valley “organic” wine with the following very colorful adjectives: “Tire on fire … smoky, rubbery, junkyard dog, rusted old car, motorshop … burnt rubber component with shallow fig and hint of peach fuzz.” The respected critics at Wine Enthusiast gave the same wine a score of 93 out of 100, while Vaynerchuk scored it 82.
How can we detect smells that were not purposefully placed there by the winemaker? After all, for all of Vaynerchuk’s hyperbole and entertainment value, did the winemaker put rubber, figs or peach fuzz into the wine that Vaynerchuk tasted? Of course not. Then why can we sense these seemingly infinite variety of aromas in different varieties of wines?
An article by physical chemist and spectroscopist Jonathan Sarfati, Ph.D., “Olfactory design: Smell and spectroscopy,” has the highly technical explanation (for those who are scientifically inclined). Dr. Sarfati published a less-technical version of this paper in his book, By Design: Evidence for nature’s Intelligent Designer—the God of the Bible. Dr. Sarfati explains on page 43–44 of the book:
Our sense of smell is actually a complex system designed to detect thousands of chemicals. It helps warn of us of danger, e.g. rotting food — we can sense one component of rotten meat, ethyl mercaptan, at a concentration of 1/400,000,000th of a milligram per litre of air. Smell also helps us distinguish types of foods and flowers. The sense of smell is actually responsible for most of the different ‘tastes’ of foods.
If the winemakers don’t doctor up their grape wines with lemon zest, cherries, chocolate, tobacco or dog hair, why do we “taste” these in the wines we drink? Dr. Sarfati cites biophysicist Dr. Luca Turn’s theory that the smell sensors in our noses are detecting the energy at which these different chemical molecules vibrate. On page 44, Dr. Sarfati explains,
This energy depends on the chemical make up — certain groups of atoms have similar energies. Chemicals with sulfur-bonded to hydrogen tend to vibrate similarly and so often have ‘rotten egg’ smells—rotten eggs themselves produce such chemicals.
Turin’s theory was supported by the rotten egg smell of certain rocket fuels (boranes) — they have nothing in common with sulfur compounds except for similar vibrations.
These “vibrations” — combined with additional sensory information obtained from our taste buds such as sweet v. sour, bitter v. salty — helps explain why the writer for Wine Enthusiast can rate a wine a 93, while another wine critic dismissively rates the same wine as an 82.
Smell has been highly linked with perceptions of taste, which can vary between people. (See Master of Wine Tim Hanni’s TasteSQ (Taste Sensory Quotient) page.) Because of these complexities of smell and taste, some people love coffee black (tannin tolerant), while other people can only drink coffee if it’s heavily loaded with cream, sugar and hot chocolate (tannin sensitive or hypersensitive).
It also helps explain how winemakers can put their heart and soul into employing the perfect grapes (with terroir and genetics in balance), yeasts and fermentation vessels but still make wines with a “nose” some critic may compare with the “bouquet” of a wet junkyard dog.