In relation to food and beverages, the basic tastes contribute only partially to the sensation and flavour of food in the mouth — other factors include:
- smell, detected by the olfactory epithelium of the nose
- texture, detected through a variety of mechanoreceptors, muscle nerves, etc
- temperature, detected by thermoreceptors
- ‘coolness’ (such as of menthol) and 'hotness' (piquance), detected through chemesthesis
Taste buds contain the receptors for taste. They are located around the small structures on the upper surface of the tongue, soft palate, upper oesophagus and epiglottis, which are called papillae.These structures are involved in detecting the five (known) elements of taste perception: salty, sour, bitter, sweet, and umami. This last, newly discovered flavour, which means ‘savoury’ in Japanese, can be detected in miso, soy sauce and other Asian foods, particularly those that contain monosodium glutamate. Scientists suspect that there are receptors for other flavours as well.
Sweet, umami, and bitter taste is triggered by different molecules that bind to the G protein-coupled membrane receptors; while saltiness is from Na+ ions and sourness is from H+ ions entering the cell.
For many years it was thought that the human tongue could be divided into neat sections according to taste receptors – the tip of the tongue for sweet, the sides for sour and salty, and the back of the tongue for bitter. However recent studies show that while scientists still have much to learn about receptors, this neat division, at least, is wrong.
Charles S. Zukeret al published a study in Nature entitled ‘The cells and logic for mammalian sour taste detection’ in which the scientists reported that receptors for the basic tastes are found in distinct cells, and that these cells are not localised but spread throughout the tongue.
However, other studies suggest that some parts may be more sensitive to certain flavours, and that there may be differences in the way men and women detect sour, salty and bitter flavours. Ultimately, receptors for different tastes are not confined to certain parts of the tongue.
Taste distortions, such as dysgeusia (persistent abnormal taste), are more common than significant taste loss, such as ageusia (complete loss of taste), and when present are more likely to have secondary adverse effects such as anxiety and depression. Taste disorders can be commonly caused by injury to the tongue mucosa and taste receptors, injury to the cranial relaying taste information, aging, radiation, toxins and medication.
Related posts:
Super Taster vs. Non Taster: Does it Matter for Your Health?
A Matter of Taste – The Genetics of Flavour Perception
A Matter of Taste – The Neuropsychology of Flavour Perception
