Although we understand the physiology of the olfactory epithelium, the organ where volatile aroma compounds are converted in to the electrochemical signals that we perceive as aromas, smell or olfaction is still largely a mystery. For example, we have 400 types of olfactory receptors but we don’t know which volatile aroma compounds activate the majority of them.
As research continues to shed more light upon how our sensory systems function – we’ve tossed out the erroneous tongue map, a diagram of taste zones on the tongue that was based on misinterpreted research – recent discoveries reveal that our tongue plays a much larger role in the perception of flavor throughout our lifetimes. Flavor being defined as the perception of aromas and tastes combined with the sensation of textures and temperatures.
At the Monell Chemical Senses Center in Philadelphia, PA, a recent study revealed that we have both taste and aroma receptors on our tongues. The research was inspired by a child’s curiosity about how snakes use their tongues to sense their environment. Being equipped to respond to volatile aromas compounds or odorants means that your tongue also plays a role in the perception of aromas.
Until now it was thought that gustation or taste and olfaction were mutually exclusive systems sending signals through separate neural pathways to their respective cortexes only to be synthesized after they arrived.
When researchers at Monell discovered olfactory receptors side by side with flavor receptors in our taste buds, their discovery demonstrated that the initial cross talk of taste and aroma information may in fact occur there first.
At the very least, they have proven there are multiple pathways for the transmission of electrochemical signals to the olfactory cortex and we’ll certainly see more research further exploring how closely the perceptions of aromas and flavors are linked.
In addition to being the location of our taste buds, the organs where aroma and flavor compounds are processed, we’re learning more about the physiology of our papillae, the bumps on our tongues that most people inadvertently refer to as taste buds.
Three out of four types of papillae – fungiform, foliate and circumvallate – host taste buds. The fourth type, filiform, doesn’t have these receptors. Fungiform papillae have a higher concentration of taste buds all of which will decrease in number and change in shape becoming more closed as we age.
When papillae are open, it’s easier for aroma and taste compounds to come in to contact with the receptors where they are processed. Closed papillae reduce the contact area between these compounds and receptors resulting in diminished perception.
According to findings by researchers at Cardiff Metropolitan University, an active lifestyle and healthy diet, one that includes low to moderate consumption of the five tastes – sweet, sour, salt, umami and bitter – could help to slow down the changes that occur in papillae as we age.
For those of us who routinely bathe our tongues in the acids, tannins and alcohol found wine, it begs the question, “How will a high level of exposure to these compounds impact our ability to perceive tastes and aromas over time?” What we do know is that your general state of health plays a significant role in the ability to smell and taste at any age.