sensory organs, called taste buds
or gustatory calyculi
, and concentrated on the upper surface of the tongue
, appear to be receptive to relatively few chemical species as tastes. This contrasts markedly with the sense of olfaction
, where very large numbers of different species can be differentiated.
There are currently thought to be five basic tastes:
- Saltiness, produced by the presence of sodium chloride (and to a lesser degree other salts).
- Sweetness, produced by the presence of sugars.
- Sourness, produced by acids.
- Bitterness, produced by alkaloids and other chemicals.
- Savoriness or umame, produced by the free glutamates commonly found in fermented and aged foods, and in the additive MSG (monosodium glutamate).
Until recently, most Western sources listed only the first four of these flavors; in recent years, umame
has become widely although not universally accepted. In China, spicy
instead of savoriness
is considered as one of the five basic tastes.
For many years, books on the physiology of human taste contained diagrams of the tongue showing levels of sensitivity to different tastes in different regions.
There is no scientific foundation for these "maps", which were based on a misinterpretation of old research.
In general, the sense of taste is often confused by smells that occur at the same time, and much of the everyday sensation of taste is at least partially derived from smell stimuli. Loss of the sense of smell (anosmia), for example when one has a cold, severely reduces one's sense of taste.
Monell chemical senses center: http://www.monell.org/