How do we taste?
Taste is one of the five basic senses. Flavour is detected by combination of taste and smell. We detect the taste of food through taste cells. Taste buds contain about 100 taste cells and are located in structures on the tongue called papillae. The papillae can be seen on the tongue as pinkish bumps, particularly around the edge of the tongue, and can be more easily seen after drinking milk.
Each taste cell has a taste pore that is capable of detecting several tastes. The five basic tastes are sweet, salty, sour, bitter and umami (meaty, savoury). The taste cell contains receptors which bind chemicals responsible for sweet, bitter and umami. When these chemicals bind to their specific receptors they activate a pathway in the taste cell which sends a signal to the brain, telling us what the food tastes like. Salty and sour tastes are detected differently by the taste cells. Sodium ions in salt enter taste cells through a channel. Acid is mainly responsible for the sour taste and it is the hydrogen ions that trigger the taste cell to send impulses to the brain.
The taste map (or tongue map) which associated each basic taste with a region of the tongue, originated from a German paper in 1901 which was mistranslated into English. The map has since been scientifically disproven. We now know that each basic taste can be detected all over the tongue where there are taste buds.
The brain taste map
For our brain to perceive different tastes the taste cell receptors must send a signal to the primary taste cortex (centre) in the brain. Very recently, scientists mapped the areas in the taste cortex that were activated for each of the five tastes. Each taste signals to it’s own separate area in the brain within a region where all tastes are perceived (the gustatory cortex). Although there is no evidence for a taste map on the tongue, there is now proof a taste map does exist in the brain. This is called the gustotopic map in the brain.
Some people (25% population) are ‘supertasters’ and can detect tastes at a lower level than normal. Scientists have discovered differences in the genes that code for the bitter taste receptor that account for this variation in bitter sensitivity. As a test to study this, scientists use chemicals such as phenylthiocarbamide (PTC) or 6-n-propylthiouracil (PROP) which only supertasters perceive as extremely bitter. Non-supertasters detect a slight bitter taste or no taste at all. Supertasters are more likely to be women than men, and to be of Asian, African or South American descent. Children are more sensitive to bitter tastes than adults, which may explain why they don’t like vegetables such as brussel sprouts and broccoli. It is also thought that supertasters have more papillae than non-supertasters.
You can find out if you are a supertaster at: