Did You Know That "Spicy" is Not a Taste?
"Spicy" is not a taste, but you didn't know that, did you?
Yes, you heard me right! Spiciness is not a taste!
You may think you know what you are talking about and perhaps you are right. The Chicken Tortilla Soup you had today may be spicy, but spiciness is not one of the five basic tastes. There are only five basic tastes and they are: saltiness, sourness, sweetness and bitterness and umami. All the other tastes are a combination of the above five basic tastes.
But here is the thing: spiciness is not produced as a result of the combination of the basic tastes. Interesting, right?
Before explaining how you perceive spiciness, let me tell you a little about how we perceive taste.
How Do We Taste Things?
Taste is basically the sensation that you get when you put something in your mouth. But that something must react chemically with the taste receptors in your mouth for you to taste it. Don't worry if you don't know what taste receptors are, just read on and you will understand.
I am going to tell you a little about the anatomy of the structures that enable us to taste food because without understanding the anatomy you won't understand the physiology of taste!
Anatomy of Taste
Stand in front of a mirror and look at the surface of your tongue. You will see that it is covered with numerous tiny knobs. These knobs are called papillae. There are four kinds of papillae: fungiform, filiform, foliate, and circumvallate. Except for the filiform papilla all the other contain numerous tastebuds.
Taste buds are small onion-shaped structures made of about 50-100 modified epithelial cells. There are two types of cells: gustatory or taste cells and sustentacular, or supporting cells.
The gustatory cells are the main cells that are responsible for transferring the sensation of taste to the brain.
On top of these cell are numerous microvilli or gustatory/taste hairs. These taste hairs contain numerous receptors called taste receptors.
The body and lower portion of the gustatory cells are attached to numerous nerve fibres. These nerve fibres are branches of the facial, glossopharyngeal and vagus cranial nerves.
The sustentacular cells are basically the supporting cells which maintain the onion shaped structure of taste buds. They are mostly located in the outer region of tastebuds.
The outer tips (top part) of these two types of cells are arranged in such a way that a taste pore is formed on the upper portion of the tastebuds. The taste hairs present on the gustatory cells protrude into these taste pores and reach the mouth cavity.
That's all the anatomy you need to know for now to understand how we perceive taste. Now let's take a look at what actually happens when you put something tasty in your mouth.
Physiology of Taste
When you put food in your mouth, the chemicals responsible for the taste of that food are dissolved by the saliva and are carried to the taste pores.
Once these chemicals reach the taste pores they bind with the taste receptors present on the taste hairs. This causes stimulation of the gustatory cells which in turn causes stimulation of the nerve fibers attached to the gustatory cells. These nerve fibers carry the signal to the gustatory cortex of the brain which interprets the signal and makes you aware of the taste.
And that is the basically how you taste something.
How Do We Taste Spicy Food?
Technically speaking we don't actually taste the spiciness in spicy food! Spiciness is in fact a form of pain sensation! Surprised? To understand why it is a pain sensation we need to know a bit of how we perceive pain.
So How Do We Perceive Pain?
Pain is basically a protective mechanism of the body. Pain makes you aware of something that is damaging your body. It makes you move away from something that is causing damage to your body.
Just like how we perceive taste via the taste receptors present on the taste hairs of gustatory cells, we perceive pain via pain receptors. These pain receptors are also called nociceptors.
Nociceptors are mostly present on the outer layers of the skin and mucous membranes of the eyes, nose, mouth, etc. But they can also be found on some deeper structures like the periosteum, arterial walls, etc.
Anatomically or structurally speaking, nociceptors are just free nerve endings.
When something damages your body, these nociceptors become activated and sends signals to your brain which intreprets the signals and makes you feel pain so that you try to move away from the source of damage.
Generally speaking, three kinds of stimuli can activate nociceptors- mechanical, thermal and chemical.
A Little About the Three Stimuli That Cause Pain
Have you ever suffered from back pain? That's an example of mechanical pain. Did you ever burn your hand while cooking? That's an example of thermal pain.
So that leaves us with chemical pain, and I guess you already know where I am going with this, don’t you? Yes, spicy foods contain chemicals which actually irritate and stimulate the nociceptors present in our mouth and the pungency you feel depends on the amount of pain it inflicts on the nociceptors. And that's not the whole story! Nociceptors, as I have said, are basically free nerve endings and in the mouth they are the free endings of the trigeminal nerve. Some of the free nerve endings of the Trigeminal nerve also monitor temperature (thermoreceptor) and spices also stimulate some of these thermoreceptors in your mouth. And that is why you also get a burning (hot) sensation while eating spicy food!
So spiciness is basically a combination of the pain and burning sensation that you get when you eat spicy food! The process of how all this happens is called Chemesthesis.
What Is Chemesthesis?
"Chemesthesis" is defined as the chemical sensibility of the skin and mucus membranes. Chemesthetic sensations arise when chemical compounds activate receptor mechanisms for other senses, usually those involved in pain, touch, and thermal perception. These sensations can be aroused from anywhere on the skin and mucous membranes of the nose, mouth, eyes, etc. That is why when you put chili pepper on your skin or nose (!) you feel a sensation of heat (burning sensation). But of course it is harder for the chemesthetic receptor on the skin to become activated by chili pepper because the surface of the skin is covered by a layer of dead skin cells whereas the mucous membranes lack this barrier of dead cells.
So, technically speaking, spiciness is not a taste because it is not produced by taste buds and the nerve that carries the "spicy" signals to the brain is the trigeminal nerve whereas taste sensations are carried via the facial, glossopharyngeal, and vagus nerves.
More Fun Facts
- Do you know why you cry when you cut onions? It's also a form of chemesthetic sensation!
- The coolness of the menthol in your mouthwash is also because of chemesthesis!
- Do you know that metallic is considered to be a basic taste as it can not be produced by combining the five basic tastes! Blood has a metallic taste.
- Do you know that scientists are now thinking fattiness could be another basic taste?