Introduction
Tasting, along with seeing, hearing, smelling and feeling, belongs to the five senses of the human being. Man is capable of tasting to check food and to stay away from poisonous things, such as plants, which are usually extremely bitter. In addition, the secretion of saliva and gastric juice is affected: it is stimulated by the sense of taste.
We are generally able to differentiate five different tastes. One of these basic human taste sensations is sweetness, which is due to sucrose (household or crystal sugar), glucose (dextrose) and saccharin (synthetic sweetener). The sour taste comes from hydrochloric acid and citric acid.
- Sweet,
- Sour,
- Bitter,
- Salty and
- Umami.
Something is perceived as bitter if it contains quinine sulfate or nicotine. If an ingested food tastes salty, this is caused by sodium chloride or calcium chloride. In addition, it is also possible to perceive mixtures of the basic tastes, such as sweet and sour.
There are discussions about whether we can also taste alkaline (soapy) and metallic tastes. In the meantime, it is also assumed that sodium salt (glutamate) is one of our taste qualities. This is referred to as the so-called umami taste.
All these flavors can trigger certain mimic reactions in us humans, which are innate and can therefore even be observed in newborns. All taste qualities adapt within certain periods of time. This means that in the constant presence of a certain flavoring substance, we no longer perceive the taste so intensively after seconds or minutes.
Only the bitter taste can be tasted to its full extent for hours, as in the past this was of decisive importance for the recognition of bitter poisonous plants and thus for their survival. In the past, it was assumed that each specific taste quality could be assigned to a fixed area on the tongue, such as the sweet taste of the tip of the tongue. However, this has now been disproved.
But how is it now possible to taste with our tongue? Responsible for this are our taste organs, the taste papillae and the taste buds, which are not perceptible with the human eye. If we take a closer look at the structure of the taste buds, we can distinguish three different types.
All taste buds, however, look like a “wall” on closer inspection, which is bordered on the right and left by a “trench” each. The so-called fungal papillae (Papillae fungiformes) are the largest group and are distributed over the entire tongue. In addition, there are leaf papillae (Papillae foliatae), which can be found on the back edge of the tongue.
Wallpapillae (Papillae vallatae) are mainly found in the back of the tongue and form the smallest group of taste papillae. Taste buds are located in the “ditches” and walls of the “wall” of the taste buds. Their number decreases slightly with age.
They contain the actual sensory cells, which in turn have receptors that are responsible for the perception of the different tastes. A sensory cell has receptors for different taste qualities. Smallest food components can bind to these receptors.
The mechanism of binding can be imagined like a key and a matching keyhole. A certain component of our food can bind to a suitable receptor of the sensory cell. Molecular processes lead to a change in the activity of the nerve fiber, which forms a connection between the sensory cells and certain areas of the brain. Thus, a signal is transmitted via the nerve fibers via several stations to the cerebral cortex, the limbic system (processing of emotions and control of instinctive behavior) and the hypothalamus, a section of the diencephalon.
