We may have got the tongue's taste map wrong

Eating is human instinct.

Especially for foodies like Pang Ke, tasting all kinds of delicious food is definitely a great pleasure in life. Whether it is a home-cooked meal made by mom or a variety of "high-end" ingredients cooked by a chef, how do we taste different flavors from different foods? When we are happy, we eat to our heart's content, but when we are sad, we have no idea what is going on. What has changed our sense of taste?

Today, Pangke will talk to you about things related to eating.

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How do you “taste” the flavor?

Why can people taste flavors? Seeing this question, my friends will definitely curl their lips: Everyone knows this, of course it’s with the tongue!

The structure of taste buds

The tongue is a muscular organ located at the bottom of our mouth. It is composed of skeletal muscles interwoven in three different directions: longitudinal, transverse, and vertical. The surface is covered with mucous membranes, and the "well-known" taste buds are distributed in the mucosal epithelium on the surface of the tongue. Taste buds are the taste receptors of the human body, composed of taste cells, supporting cells, and basal cells. When flavorful substances (taste substances) come into contact with taste cells, they can stimulate the receptors to generate electrical signals, which are transmitted to the nerve center to produce taste.

The Five Elementary Flavors of Taste

As we all know, the colorful world we can see is actually produced by a mixture of three colors: red, green and blue. These three colors that cannot be decomposed any further are what people call the three primary colors of optics.

So, is there something similar to the three primary colors in taste?

The answer is yes.

Studies have shown that humans can distinguish 4,000-10,000 different flavors. Although the tastes of these flavors vary greatly, they are essentially composed of the five basic taste combinations of salty, sour, sweet, bitter and umami, which are equivalent to the "five basic tastes" of taste.

Among them, the four tastes of salty, sour, sweet and bitter are familiar to everyone and easy to distinguish, but what exactly is the taste of "fresh"?

Umami is a light but indescribable long-lasting taste. The most commonly used ingredient in our lives is "MSG". Its main ingredient is monosodium glutamate, a type of amino acid. The umami taste felt by the tongue is actually the taste of amino acids. Humans and animals have special receptor cells on their tongues that can detect carboxylate anions of amino acid salts, which is the source of umami.

Since we are talking about basic taste, we have to mention a widely circulated saying: taste buds in specific areas of the tongue are responsible for a specific taste, the tip of the tongue is responsible for "tasting" sweetness, the root of the tongue is responsible for "tasting" bitterness, and sourness and saltiness are "tasted" by the sides of the tongue...

However, surprisingly, this "taste map" that many people believe in is actually a misunderstanding.

The taste buds in different parts of the tongue have different sensitivities to different tastes. Generally speaking, the taste buds at the tip of the tongue are more sensitive to sweetness, the taste buds on the sides of the tongue are more sensitive to sourness, the front of the tongue is more sensitive to saltiness, and the root of the tongue and a small number of taste buds distributed in the soft palate are more sensitive to bitterness.

In 1974, the research results of American scientist Virginia Collings completely broke the "rumor" of "taste map". She dripped various flavors of different concentrations into different areas of the volunteers' mouths, and finally concluded that each area of ​​our tongue can taste 5 basic tastes, but different areas have different sensitivity thresholds to each taste.

So, the real taste map should be like this:

(Copyrighted stock image, no permission to reprint)

Can a person's sense of taste change?

From a physiological point of view, the taste qualities of different flavors are actually different types of "external stimuli". For example, sour taste mainly comes from hydrogen ions, salty taste mainly comes from the stimulation of metal ions such as sodium and potassium, and substances with other tastes such as "sweet", "bitter" and "fresh" will respectively bind to their corresponding G protein-coupled receptors and trigger corresponding neural electrical signals.

As the "receivers" of taste, our taste buds are not static.

Generally speaking, as people age, the number of taste buds on the tongue surface gradually decreases, and their functions also decline. Clinical studies have found that people over 60 years old are much less sensitive to salt, sucrose and other substances than those aged 20-40. Interference from factors such as disease, drugs, and smoking can also lead to taste dysfunction or even loss.

However, for most people, what is more common in daily life is "cross-taste", which is a temporary change in taste function. For example, local anesthesia can cause people to temporarily lose their sense of taste, while other substances can inhibit or enhance one or more tastes.

I believe that many of my friends have had the same experience as Pang Ke: when you eat fruit immediately after brushing your teeth, the originally sweet and sour fruit will become bitter and astringent... We are just brushing our teeth, have we damaged our tongue?

In fact, this is most likely related to a surfactant called sodium lauryl sulfate (SLS) in toothpaste. Scientists believe that SLS can inhibit sweet receptors and activate bitter receptors, and the effect can even last for 1 hour.

The "original purpose" of taste is to judge the nutritional value of food and avoid ingesting poisons. With the development of human civilization, taste has taken on an additional meaning, which is to allow us to enjoy the pleasure brought by delicious food.

What other experiences do you have regarding the "cross-flavor" of food? Feel free to leave a message in the comment section and have a friendly exchange with fellow foodies Pang Ke!

Creative team: China Science and Technology Museum New Media Team

Review expert: Lu Bin, deputy chief physician of the Stomatological Hospital of Air Force Medical University