The Physiology of Taste

The Science of Taste and What It Means to Coffee

The world has been curious about taste for thousands of years. This curiosity stems from a universal yearning to get more pleasure out of the food and drink that we consume. It’s only with a better understanding of taste that we can make things tastier. The problem is that all of these efforts have been dramatically hampered by a fundamentally flawed assumption about taste at the theoretical level. Until this basic assumption is corrected, there is only so far we can go in maximizing the satisfaction we get from food, wine and perhaps most importantly, coffee.

Before I became a chef, I was pre-med at Yale with a particular fascination in molecular biochemistry and biophysics. My junior year, I enrolled in a course on the physiology of taste and what I learned was so enthralling that it rerouted my career course into the culinary world. The revelation? That our palate measures all taste relative to what immediately preceded it and in relation to our environment.

We have been under the misimpression, for a long time, that taste works in a static model, like a piece of laboratory equipment. When you stick a thermometer into different bodies of water, it will consistently give you a reliably accurate temperature, relative to an absolute scale (such as Kelvin T=0). The assumption with taste is that our palate can be relied upon like a thermometer, to register sugar, bitter, acid, and so on, in a consistent fashion; and, with faithful relationship to some absolute scale. We now know, beyond any question, that is the opposite of the truth.

Take something sour, for example. Your tongue, and all of the mucous membranes in your mouth, cannot tell you that this substance has a pH of 2.2 or 5.1. All it really can tell you is that something is more sour or less sour than the substance we were just tasting a few seconds ago. This can be easily demonstrated with a lemon wedge and water. Have several tastes of water, swishing it around your mouth, until you feel it’s equilibrated. When the water tastes like water, bite into the lemon, moving the juice all around your mouth so that every surface of mucus membrane has some exposure. Then, go back to the water and taste it, and what is astonishing is that the water will taste sweet, as if you’ve added 2 tablespoons of sugar. The water hasn’t changed all, just your palate’s reference point.

In other words, if you consume something with a high degree of a specific flavor, it will reduce your palate’s ability to detect that same flavor in the subsequent substance, while amplifying opposite flavor qualities. For example, if you eat something very sweet and then taste coffee that is naturally sweet as well, like an Ethiopian Yirgacheffe, the coffee will appear to have less residual sugar, and the opposite qualities – bitterness and acidity – will be more prominent. You can imagine the effect this would have on everyone that drinks coffee with maple syrup-drenched pancakes at breakfast.

Another big component of taste that affects our coffee experience is external environment. Consider this: most of taste is smell. There is a massive difference between the smell of something that’s not yet in your mouth (ortho-nasal) versus the smell as you are chewing and the aroma is climbing up into your sinus cavity (retro-nasal). The same exact substance has a different aromatic profile depending on those two things. So while your favorite coffee will have a consistent smell ortho-nasally, once sipped, the taste you experience depends on the reference point of your palate, which can be drastically altered by external aromas.

If the opportunity allows it, take a coffee that you know well and pay attention to how it tastes at the beach, where the heavy brine and salt ions in the air fatigue your taste buds, or in the woods, where earthy, terrestrial aromas distort your palate, or even at high altitudes where our papillae register sweet by 30% less, and where the temperature at which water boils is 2°F less for every 1,000 feet of elevation (just imagine what a 16° cooler boiling point means for your coffee extraction at 8,000 ft.). The coffee will be unsatisfactory, not because of anything inherent, but because of the effect of the external environment on our taste perceptions and even on the brewing process itself.

The most complex fine wines rarely have more than 250 volatile molecular compounds contributing to their remarkable bouquets – but, the Maillard reactions in the roasting process of a fine coffee can produce more than 800 flavor and aroma compounds. At its best, coffee can be a beverage of amazing richness and elegant complexity.

It’s only been a few decades since we’ve just begun to penetrate the mysteries of the neurochemistry of taste and smell. There is still so much to be discovered, but what we do know with certainty is that all flavor and aroma have a dynamic affect on the next thing we experience. Creating, and even consuming coffee, without understanding these principles limits the potential of our coffee enjoyment. Only by being sensitive and aware of how the environment around us affects taste, can we take the next step in making coffee even more satisfying.

By Craig Shelton, a James Beard award-winning chef and founder
of King’s Row Coffee

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