A bitter pill, sour grapes, or sweet nothings – descriptions of taste are often associated with strong emotions. They express in words states of intense pleasure as well as displeasure.
This strong link connecting taste with emotion and drive has to do with our evolution: Taste was a sense that aided us in testing the food we were consuming. It was, therefore, a matter of survival. A bitter or sour taste was an indication of poisonous inedible plants or of rotting protein-rich food. The tastes sweet and salty, on the other hand, are often a sign of food rich in nutrients.
Sweet, sour, salty, bitter – and savory
Savory dishes that taste of broth evoke pleasant emotions in most people. They are a signal that the food is rich in protein. This flavor has been recognized as the fifth raw taste and the four better-known sweet, sour, bitter, and salty tastes. There are sensory cells specifically for this fifth taste that a Japanese researcher discovered around 1910, so the common Japanese term umami is used for “savory.”
Taste, smell, and flavor
What is generally categorized as “taste” is a bundle of different sensations: it is not only the qualities of taste perceived by the tongue but also the smell, texture, and temperature of a meal that is important. The “coloring” of a taste happens through the nose. Only after taste is combined with the smell is a food’s flavor produced. If a stuffy nose impairs the sense of smell, the perception of taste is usually dulled. Like taste, our sense of smell is also closely linked to our emotions. This is because both senses are connected to the involuntary nervous system. That is why a bad taste or odor can bring about vomiting or nausea. And flavors that are delicious increase the production of saliva and gastric juices, making them truly mouthwatering.
The sense of taste: from the right mix
Based on the information transported from the tongue to the brain, there are thought to be at least five essential taste qualities. Many dishes are made up of a combination of different flavors. Some dishes taste sweet-sour, for example, while others are salty and savory. The primary flavors are:
We perceive that sweetness is usually caused by sugar and its derivatives, such as fructose or lactose. But other types of substances can also activate the sensory cells that respond to sweetness. These include some protein building blocks like amino acids and even alcohol in fruit juices or alcoholic drinks.
It is mostly acidic solutions like lemon juice or organic acids that taste sour. Hydrogen ions, chemical symbol cause this sensation: H+, split off by an acid dissolved in a liquid solution.
Food containing table salt is mainly what we taste as salty. The chemical basis of this taste is the salt crystal, which consists of sodium and chloride. Mineral salts like the salts of potassium or magnesium can also cause a sensation of saltiness.
Many fundamentally different substances bring about a bitter taste. In total, there are about 35 other proteins in the sensory cells that respond to bitter substances. From an evolutionary standpoint, this can be explained by the many different bitter species of plants, some of which were poisonous. Recognizing which ones were indeed poisonous was a matter of survival.
The “umami” taste, which is somewhat similar to the taste of a meat broth, is usually caused by glutamic acid or aspartic acid. These two amino acids are part of many different proteins found in food and also in some plants. Ripe tomatoes, meat, and cheese all contain a lot of glutamic acids. Asparagus, for example, contains aspartic acid. Chinese cuisine uses glutamate, the glutamic acid salt, as flavor enhancers. This is done to make the savory taste of foods more intense.
Fatty, alkaline, water-like: What else can we taste?
Researchers are looking for other sensory cells specialized for sensations besides the five established basic tastes. There are thought to be more:
Fatty: People used to think that the preference for fatty foods was based solely on their smell and texture. Newer research suggests that there are probably receptors specifically for fat. This would make fatty the sixth raw taste. Certain fatty acids cause that enzymes in the saliva to split from fatty foods. A specific receptor has been discovered that responds to linoleic acid, which is part of many triglycerides found in natural fats and oils such as sunflower oil, soya bean oil, or corn oil.
Research is currently being done on these tastes:
Alkaline: as in brine, and the opposite of sour
Hot or spicy is not a taste.
By the way: the sensation of something as “hot” or “spicy” is quite often described as a taste. Technically, this is just a pain signal sent by the nerves that transmit touch and temperature sensations. The substance “capsaicin” in foods seasoned with chili causes a feeling of pain and heat.
Bitter in the back, sweet in front: A common myth
There is a long-held misconception that the tongue has specific zones for each flavor where you can taste sweet or sour, for example, exceptionally well. But this myth is based on an incorrect reading of an illustration of the tongue. You can still find these zones in many textbooks today.
All parts of the tongue can sense sweet, sour, salty, bitter, and savory tastes. Only the sides of the tongue are more sensitive than the middle overall. This is true of all flavors – except that the back of our tongue is susceptible to bitter tastes. This is apparently to protect us from spitting out poisonous or spoiled foods or substances before entering the throat and are swallowed.
It starts at the tongue: From substance to taste.
But what is taste? What happens in our body that enables us to perceive flavor? The chemical substance responsible for the taste is freed in the mouth and comes into contact with a nerve cell. It activates the section by changing specific proteins in the wall of the sensory cell. This change causes the sensory cell to transmit messenger substances, which in turn activates different nerve cells. These nerve cells then pass information for a particular perception of flavor on to the brain.
The numerous wart-like bumps on the tongue’s mucous membrane are where the substance producing the taste is transformed into a nerve signal. These bumps, which are called taste papillae, contain many sensory cells with a unique structure: together with other cells, they make up a bud that looks a bit like an orange with its sections arranged around a center.
In the middle of the top side is a small indentation filled with fluid. The chemical substances responsible for the taste are washed into this funnel-like hollow. This makes sure that the senses are detected and analyzed by as many sensory cells as possible before being swallowed.
What are the taste papillae?
The taste papillae are a good number of wart-like bumps under the mucous membrane of the tongue. They increase the tongue’s surface area several times and make sure that individual tastes can be perceived more intensely. This is also called the magnifying effect of the language. The papillae contain several taste buds with sensory cells.
There are three types categorized by their shape:
Fungiform papillae are the most common: between 200 and 400 bumps are spread all over the tongue’s surface. They are found mostly at the tip of the language and at the edges, where they make sure that these areas are especially sensitive to taste. Fungiform papillae not only detect taste, but they also contain sensory cells for touch and temperature. Each papilla contains 3 to 5 taste buds.
Circumvallate papillae are very large and found at the base of the tongue, where the throat begins. Every person has only 7 to 12 circumvallate papillae, yet these papillae each contain several thousand taste buds. Circumvallate papillae are round, raised, and visible to the naked eye. They are arranged in the shape of a V at the back of the tongue. These papillae are called circumvallate papillae because they are surrounded by a trench containing many glands that “rinse” the taste-producing substances into the sensory cells.
Foliate papillae can also be seen with the naked eye on the rear edges of the tongue. There you can see several folds that lie close together. Our language has about 20 foliate papillae, each of which has several hundred taste buds.
What are the taste buds?
Taste buds are the real taste organ. They have numerous sensory cells that are, in turn, connected to many different nerve fibers. Each taste bud has between 10 and 50 sensory cells. These cells form a capsule that is shaped like a flower bud or an orange. At the tip of this capsule, there is a pore that works as a fluid-filled funnel. This funnel contains thin, finger-shaped sensory cell extensions, which are called taste hairs. Proteins on the surface bind chemicals to the cell for tasting. The taste buds are located in the walls and grooves of the papillae. Adults have between 2,000 and 4,000 taste buds in total. The sensory cells in the taste buds are renewed once a week. Most of the taste buds are on the tongue. But some cells detect taste elsewhere inside the oral cavity: in the back of the throat, epiglottis, the nasal cavity, and even in the upper part of the esophagus. Infants and young children also have sensory cells on their hard palate, in the middle of their tongue, and their lips and cheeks’ mucous membranes. The final step in perceiving taste is transferred to the nervous system. Several cranial nerves do this. All information is carried along the cranial nerves to part of the lower section of the brainstem (the medulla oblongata). At that point, there is a split: Some fibers carry taste signals together with signals from other sensory perceptions like pain, temperature, or touch through several exchange points to consciousness. The different fibers pass over these exchange points of conscious perception and lead directly to the brain’s parts connected with sensory perception and are responsible for securing our survival. It is here that taste signals are combined with different smell signals.
A virtually limitless palette of flavors
About half of the sensory cells react to several of the five basic tastes. They only differ by having varying levels of sensitivity to the different basic tastes. Each cell has a specific palette of flavors with fixed rankings: this means that a particular cell might be most sensitive to sweet, followed by sour, salty and bitter, while another has its hierarchy. The full experience is produced only after all of the sensory cell profiles from the tongue’s different parts are combined. The other half of the sensory cells and nerve fibers are specialized to react to only one taste. These cells’ job is to transmit information on the intensity of the stimulus – how salty or sour something tastes. Assuming five basic tastes and ten levels of power, 100,000 different flavors are possible. With the senses of touch, temperature, and smell, there are many other possible flavors.
Thanks for reading! Chef W