All About Aroma

Understanding Smell

First, let’s look at the basics of smell. Humans have approximately 400 olfactory receptors in the nasal cavity. Smells bind to different receptors, activating them, and causing a message to be sent to the olfactory bulb in the brain. The olfactory bulb then communicates with the rest of the brain, interfacing with other areas including the hippocampus, neo-cortex and amygdala, which are all responsible for various aspects of memory. 

Something Smells Fishy… 

Though conventional wisdom is that humans have a worse sense of smell compared to other animals, this idea is not based on scientific or empirical evidence. Rather, it is based on a “19th-century hypothesis about free will that has more in common with phrenology than with our modern understanding of how brains work,” says Joanna Klein. 

This idea that humans have a poor sense of smell is seeing more and more opposition everyday. One study of several hunter-gatherer groups in the Malay peninsula found that those communities had far superior sense-memory recall and a much wider vocabulary to describe the odors they were smelling. These communities demonstrate that humans have a much greater ability to smell than Western thinkers originally thought. We may be limited more by our imagination than by our biology. 

“Good” Versus “Great” Smellers  

The distinction between “skilled” and “poor” smellers is becoming more and more blurred. The coffee industry itself is a great example of the way that training and practice can hone sense-memory recall and smelling aptitude. SCA Sensory and Q Arabica and Robusta courses can offer industry professionals the chance to improve their cupping skills and expand their sensory experiences. Cuppers in the industry demonstrate that the ability to match aroma to a description is not fixed but improvable. 

Sometimes, however, smell is just different. In a May 2019 New York Times article aptly entitled “You Will Never Smell My World the Way I Do,” the author writes, “It’s not that some people are generally better smellers, like someone else may have better eyesight, it’s that one person might experience certain scents more intensely than their peers.”  
The article outlines a recent study that looked at genetic code in relation to how intensely people smelled different scents. 

Remember the 400 or so different olfactory receptors in the nasal cavity we talked about earlier? Well genetic mutations can slightly alter the shape of those receptors, affecting how well a particular odor binds to them and alerts the brain to its presence. 

Another study, conducted in 2016, found a similar relationship between genetics and smell ability in relation to a specific scent: urine after eating asparagus. The study found, surprisingly, that only about 40% of the population could smell the distinct difference in urine odor caused by eating asparagus. This study identified over 870 different variations in the DNA sequence of those who could not smell asparagus in urine. They were all located on chromosome 1, a region known for a number of genes that impact smell. 

Scent Across Time and Space (And Hormones)  

One study found that the time of day actually affects your quality of smell. Two to 10 in the morning were found to be the least effective time to smell while the peak time for smelling was around 9 in the evening. (It’s important to note that this study was conducted with 12-15 year olds. However, based on existing research into human smell throughout life, it is reasonable to apply this data to older adults at this time.) 

Other research suggests that hormones and menstrual cycles affect how intensely women detect certain scents. Women who are ovulating tend to have a heightened sense of smell compared to other women while pregnant women often have increased sense of smell and may develop new aversions or affinities for particular aromas. 

Changes in smell intensity are not just linked to menstruating women, but to people of all ages and genders. Being tired or sleep deprived can affect your smell ability, so rest up!  One 2017 study found a link between the loss of smell for patients with Parkinson’s Disease and the difficulty entering REM (rapid eye movement) sleep for that same group. While people with Parkinson’s are a relatively small subset of the population, the fact that the study links sense of smell to REM sleep could suggest a larger pattern for the general population. 

Scent and Smell in Coffee 

Now that we have a better understanding of emerging research in olfactory abilities, we can extrapolate this research into the field of coffee. While we already know that people can develop their sense of smell and that our ability to smell is much greater than people initially thought, one thing that might bear further inquiry is the circadian rhythm of our sense of smell. If we smell better in the afternoon and evenings, perhaps we should work to schedule cuppings near the end of the day to maximize our ability to pick out specific odors. 

The Differences Between Us 

But what we don’t know, or perhaps think about as much, is how differences in odor perception might affect sensorial coffee grading. If everyone perceives slightly differently and has individual inclinations and aversions to specific odors, how do we standardize cupping and sensorial grading? We don’t have a solve-it-all answer for you today but we can offer a few thoughts: 

When we notice the differences in smell perception, we can better appreciate the importance of practice and calibration. Though we might not all experience smell in the exact same way, when we cup together and discuss our scores and findings, we can better calibrate our senses to align with other coffee professionals. 

One standardized approach to calibrating coffee professionals is the World Coffee Research (WCR) Sensory Lexicon. 

The lexicon includes 108 core aromas and flavors that we experience in coffee and gives concrete and exacting instructions for recreating these smells in one’s own cupping lab. By offering specific examples of a certain aroma that everyone can experience individually, we may be able to bypass the difficulty of differences in smell. Whether the “musty” aroma concoction smells more like sawdust or mothballs to someone is unimportant because they now associate that particular aroma with the description “musty” and can recall that word to describe the same aroma when they smell it in coffee. In other words, what exactly something smells like it irrelevant as long as everyone has the same reference point with which to tie the aroma back. 

Le Nez du Cafe kits offer another standardized approach by bottling particular aromas and enabling cuppers to practice matching specific aromas to names. However, the kits highlight the differences in smelling among different people. While the bottle aroma may contain the major chemical components of say, the aroma of walnut, many people find that the aroma smells more like curry powder or another completely different aroma to them. Like with the WCR Lexicon, however, this smelling difference is mitigated by the standardized reference of the Le Nez vial. So, when someone who has used the kit smells ‘curry powder’ in their coffee, they know to associate that aroma with the word “walnut” rather than “curry powder.” 

Moving Forward  

The emerging field of genetic testing may offer greater insight into how we smell what we smell. As scientists gain a greater understanding of how olfactory receptors and other mechanisms of scent work, we as coffee professionals may also gain insight into how we experience smell similarly and differently. 

As we move into the coming months and years of coffee tasting, we can make an effort to stay abreast of the new research into sensory perception as a whole. By gaining a greater understanding of the way we smell and taste, we can become better cuppers and better coffee professionals overall.