Would you believe that up until about fifteen years ago there wasn’t much? It’s true. Scientists knew virtually nothing about how the human taste sense actually functioned. Sure, we had these types of simple diagrams, but as far as determining exactly how human sensory organs intercepted and interpreted flavors, there was virtually no data. That began to change in the mid-1990’s when scientists in the US and Europe finally started to hold some long-held assumptions about taste up to scientific scrutiny. What they found was that there was far more to the perception of taste than anyone had ever imagined.
First, it won’t surprise you to learn that those tongue diagrams are mostly wrong. Not only are there more than four basic types of flavor receptors (the fifth, umami, the glutamate-sensing receptor discovered by Japanese scientist Kikunae Ikeda in 1908, has been scientifically proven to exist), but they’re scattered all over the tongue. Additionally, receptors that were once thought to perceive just a single sweet/bitter/salty sensation have been show to have far more versatility. Some half-dozen different types of “bitterness” have been discovered in the last ten years, for example. It’s also been revealed that temperature itself is perceived as flavor on the tongue, with warmth registering as faint sweetness and cold as sourness.
So, far from a simple mechanism that registers four flavors in various combinations, the tongue is slowly being seen for what it is: and incredibly subtle and sophisticated organ capable of distinguishing minute variations in what’s placed on it. This will come as old news to serious foodies, but to science it’s been a revelation. And of course the tongue is just the beginning of the taste sense. The nose and nasal membranes are every bit as important (since that’s where volatile oils are mostly perceived). But before we get into that it’s important to understand a bit more about how the tongue works. More on that a bit later.