Of all the protuberances extending from our bodies, it is our noses that are held in highest esteem when it comes to enjoying wine. The Schnoz of a trained wine professional is thought to harbor more natural capabilities than those of normal people. However, it hasn’t been until relatively recently that the world of science has begun to figure out just how is it we detect and identify odors.
A good reasoning behind this progress is that it hasn’t been until relatively recently that we have been able to begin to understand how our brains work. It turns out that the nose of a Sommelier is nothing special. In terms of hardware, we all have approximately the same level of sensitivity. Therefore, the only real major difference between the nose of an amateur and that of a professional is, like everything else in the world, the amount of practice and training. That and bravado. Professionals know that sometimes emphatically stating that something is the way they say it is, regardless of the truth, can be taken seriously. Because really, who’s to argue?
All that practice and training of course, does little to “tone” our sniffers, but more to educate the olfactory memories of our brains. That’s right, we learn how to pick out smells in the same manner we learn how to play a song. We memorize the pattern. This of course means we can mistake one smell for another in moments of error. Our memories are imperfect beasts.
Speaking of beasts, how many times have you been told that dogs or other animals are far superior smellers that we humans are? Let me please disabuse you of that notion. There are two ways to smell. One is called Orthonasal Smell which happens when suck air in through our nostrils. There is no doubt that animals with larger and longer snouts than us are superior at this kind of sniffing. More space for sensors to pick up all of those molecules. However, there is another type of smelling called Retronasal Smell which happens when we breathe out through our nose. As far as we can tell ape descendants are the only animals that have a sizeable retronasal passageway to make this kind of function useable. Therefore, we smell things before we put them in our mouths, and we also smell things (hopefully food) after they have been put into our mouths. Two smells for the price of one.
He doesn’t even care if the steak is cooked well, does he?
One could say we have a much more developed second dimension of smell. It is this secondary smell combined with the enhanced processing powers of our brains that actually make us far superior smellers that most of the animal kingdom. Interestingly, we are the only animals that appear to be concerned with the quality of the calories being put into our mouths for ingestion. It turns out that even if you have lost your sense of orthonasal smell, that doesn’t necessarily mean your retronasal smell capabilities will be affected.
So what are smells exactly? It depends upon which part we are referring to. In wine, a number of different smells that can be found in wines are handily put onto what we call aroma wheels or in lists for our reference. However, the aromas listed are actually collections of a number of different aromatic compounds which themselves are combinations of various different individual molecules.
Let’s take rosemary for example. If you were to smell the plant you would say, “This smells like rosemary.” But a more trained sniffer would say, “I smell a combination of woody and floral notes as well as some conifer, clove, and eucalyptus”. And beyond that, each of those individual aromas are either single molecular compounds or a combination of a few of them. So an aroma must be thought of as a complex object and not a single entity much like a picture. A picture after all is a collection of shapes and colors and that analogy is quite a bit more appropriate as will soon be realized. The term bouquet is perhaps more appropriate when discussing the collections or aromas in wines, but we tend to use those terms differently (if not incorrectly) in the world of wine so I will forgo its use here.
Before we recognize aromas though, they must first pass through our snouts to be captured. Again, once on the way in (orthonasal), and once on the way out (retronasal). How that happens is really still up for debate. The previous theory was that we had receptors that would accept a single odor molecule much like a key fitting into a lock. That has been modified over the years with the allowance that perhaps more than one odor molecule may fit onto a receptor. After all, we might not even have space to put a specific receptor for every single scent we can sniff. An additional theory is that the odors vibrate the receptors instead of locking into them; much like sound vibrates our ear drums. Gas Chromatography analysis of smelly things is somewhat based on this vibrational theory as it is used to identify the individual molecular compounds which it visualizes in the form of a plot of different frequencies. This looks a bit like the sound waves of an erratic melody or the EKG print out of a failing heart.
Regardless of what the actual entry method is and how much is detected, each odor received sends a unique set of signals to a portion of our frontal lobes in the brain that is formed in the shape of a light bulb aptly called the Olfactory Bulb. Because our odor sensing receptors are tuned to multiple odors, the signals flowing up will tend to have overlaps as they hit the Olfactory Bulb. The outer layer of this section called the Glomeruli is composed of individual cells, much like an LED screen which is “lit up” neurologically speaking with the pattern of the smell. fMRI studies have actually been able to watch this happen and produce visual images of smell. Yes, that’s right; when you smell a strawberry, it creates a different image in your brain, than when you smell a banana.
However, our noses have different thresholds of detectability for different aromas. For instance, TCA (2,4,6-Trichloroanisole), the odor we speak of when a wine is “Corked” can be detected when it is merely a few parts of a trillion. Diacetyl, on the other hand, which is the basis for all of the buttery and creamy aromas takes a few parts per thousand to be detected. And while there is some variation between individuals on what these thresholds are, there is perhaps more variation found depending on what kind of wine the aroma is in.
To complicate our perception of what we are smelling even further, the aromatic image that appears when we sniff can also be shaped by how we are mentally framed and primed beforehand. In other words, we can be influenced by what have smelled previously, what we are currently craving, or even what we have been told about what we are going to smell. For instance, it has been shown that even professional wine tasters have insisted that aromas exist in a given wine even though they do not just because the color of the wine they were smelling had been changed unbeknownst to them. Perhaps, no one has sneakily changed the color of your wine, but how many of us can recall a time where a particular odor, good or bad, just would not leave us and we insisted we smelled it everywhere. The nestling of our olfactory processing center so closely to our memory center helps us emotionally connect to aromas, but can also lead to confusion when too much information is presented during a sniff.
Traditionally, when it comes to wine we rely on seasoned experts to assist us in how we should perceive a wine’s aromas. While we assume that the conclusion of a practiced professional will be more consistently correct than an amateur, they are still dealing with a measurement where the human nose is more precise than any other means of measure that we have. That is to say, you can never be completely sure if the overly poetic description of a wine’s aroma is what is actually emanating from the wine or even if it is the same as what you will sense. Helpful for the general gist of what we can expect, but should be taken with a grain of salt. Therefore, when it comes to flavor matching in wine and food pairings, it is best to speak in generalities instead of specifics. The red fruits in the wine will probably bring out the red fruits in the food even if they aren’t the overripe and slightly confectioned cherries you were told to expect.
Our sense of smell, once relegated to our least powerful sense, has actually been shown to perhaps be our most affecting sense. Its connection to our memories creates emotional responses when triggered and as we uncover more about how the sense works, it is taking on a new level of dimensionality. However, the typical wine drinker should rejoice in knowing that even if we marvel at the skill a professional demonstrates when they can identify a wine at first sniff, we all smell things a little better after we have taken the first sip.
Additional sources for reading:
Neurogastronomy: How the brain creates flavor and why it matters – Gordon Shepherd
Taste Buds and Molecules: The art and science of food, wine, and flavor – Francois Chartier
Aaron Berdofe's Wine and Food Experience 