The Taste in Our Buds: The Human Physiology of Taste

I turned the wooden stick slowly until I could see the tip, sharpened fine as a pencil. As the fire crackled underneath, one lone spark caught the white fluff affixed, and I watched as it burst into a single flame. The sound of childhood excitement faded into the background and I lifted the stick and blew.

Half burnt, half raw, I, with my appetite, which had now gone from whetted to famished, placed it in my mouth and chewed slowly. The smooth tasteless coating broke into a sticky, sugary, flavorful mess: After twenty-odd years, I had tasted my first roasted marshmallow.

Though I had never experienced anything quite that texture, or, frankly, that oddly sweet before, I wondered how it was created and, further, how I was able to even taste something so clearly artificial. Of course, it has been estimated that man began “making” food (by way of cooking) some two million years ago, a marshmallow didn’t seem quite like natural food that had been cooked.  How was it that a mammal would have the capacity to taste and enjoy something it was so clearly, it seemed, not designed to consume? And yet, this marshmallow was not only consumable, but enjoyable. How?

As a chemical sensation that occurs in our mouths and throats, we human beings, much like other animals, have been equipped for evolutionary reasons with the primitive sense of taste not only to drive our appetite (which, of course, helps us feel the need to source food in order to acquire nutrients from it), but also to detect poisons in what we consume, helping to ensure that we survive in whatever environment we find ourselves in. For their nutritional value, we crave salty foods because we need sodium chloride to survive, and sweet foods because of a similar need to eat carbohydrates. Also, on the majority, we crave savoury flavours like meat to fulfill our need for amino acids. Bitter and sour tastes, however, are finely tuned in our mouths, as most poisons produce similar tastes and eating too much of them could have disastrous effects.

The human physiology behind our ability to taste, however, is complex process, which involves not only our mouths but our nose (and even eyes!), as it is the combination of taste, smell, and sight that allows for the full experience of flavour. If you hold your nose while eating, for instance, you will notice that the food you consume loses taste. And when one complains of taste loss, according to researchers at the University of Pennsylvania Smell and Taste Center, this usually, and unsurprisingly, reflect a loss of smell function. Although taste and smell are very different senses, this is primarily because the two combine in the brain to give the sensation of flavour. Interestingly, new research also implicates vision in this process, as it has recently been found that what we see informs what we taste: “Our perception of food is affected by the sensory properties of the food itself, together with our expectations about the food and other contextual factors. The latter are especially relevant in the restaurant setting, where appearance factors, such as the presentation of the food on the plates can dramatically affect food liking and consumption.” In a clever study looking at how accessories affect our perception of food, the researchers explored how the color (either black or white) and the shape of a plate on which identical strawberry mousse dessert was served would affect the perception of flavour intensity, sweetness, quality, and liking of the mousse in participants. After analyzing the results, the authors concluded: “The results demonstrated that while the colour of the plate exerted a significant influence on people’s perception of the food, the shape of the plate did not. In particular, when the mousse was served from a white plate, it was perceived as significantly more intense and sweeter, and was also liked more.”

But vision and smell aside, throughout our mouths and throats we have chemical taste receptor cells (called chemoreceptors) that cluster together to form taste buds, which are made up of about 50-100 cells. These buds are invisible to the naked eye, but sit atop taste papillae, which are what we see as the little red dots on our tongues (they are red because they are densely packed with blood vessels!) . We have four primary types of papillae, each serving a different purpose. Fungiform papillae, of which we have around 200, are found at the front of our tongues and can distinguish all five tastes. Foliate papillae, of which we have only about five, are located at the edge of our tongues and are sensitive to sour tastes. Circumvallate papillae, of which we have from three to 13, are located along the tongue and responsible for sour and bitter senses. Lastly, we are also equipped with filiform papillae, which do not have a sense of taste. On the base of the papillae are nerve endings.

We have three main nerves that communicate taste to our brains; the facial nerve, the hypoglossal nerve and the glossopharyngeal nerve, which all communicate taste from different parts of the mouth and throat. The trigeminal nerve, though it does not communicate taste, feeds our brains sensitive information about the texture and temperature of what we consume.

When we bite into a delicious marshmallow, for instance, our saliva breaks down what we eat into chemicals, which are understood by the chemoreceptors in our mouths. These chemicals bond with chemicals in our chemoreceptors, travel through our nerves into the brain and eventually reach our gustatory system (though this process happens in nanoseconds). While we only have five different combinations of taste – sweet, salty, savoury, sour and bitter – because we integrate smell and sight, we are able to distinguish between thousands of tastes, from marshmallow to mango, and everything in between!

By: Mariana Bockarova

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