What is taste? – Fifth Sense
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What is Taste?

There is a common misperception that the word ‘taste’ refers to everything we experience when we eat or drink.  This isn’t actually true.

The word taste, or gustation, to give its full name, refers to what is detected by the taste cells, located on the front and back of the tongue and on the sides, back and roof of the mouth.  These receptor cells, or taste buds, bind with molecules from the food or drink being consumed and send signals to the brain.  The way our brains perceive these stimuli is what we refer to as taste, with there being five recognised basic tastes: salty, bitter, sweet, sour and umami.

Some scientists think that there are other tastes we are capable of perceiving.  A study published in July 2015 indicates that fat may be a taste in its own right.  There is also debate as to whether metallic tastes are actually a true taste or are the result of reactions between different metals present in saliva.  A metallic taste in the mouth can actually be an indicator of a taste disorder.  To date no specific receptor cell has been discovered for metallic tastes.

Kokumi is something that is producing much debate in scientific circles.  There is no evidence to support it being a basic taste in its own right, and is often described as a sensation; ‘richness’, ‘thickness’, ‘heartiness’.  It is thought that it is actually more of a ‘taste-enhancer’, amplifying and balancing other taste elements in certain foods.  Prof Barry Smith of the Centre for the Study of the Senses and Chef Jozef Youssef of Kitchen Theory are working together with the aim of better understanding kokumi.  New Scientist magazine published an article on this whilst Jozef has written a short piece on this mysterious sensation here.

Taste and flavour

The five basic tastes covered above do not, of course, give the complete picture of what we experience when we eat or drink.  Take mint, for example; our perception of mint cannot be readily assigned to one of the five categories above, although it does contain an element of bitterness and also trigeminal nerve stimulation (the sensation of ‘coolness’ in the mouth).  There is, of course, a whole realm of sensation available to us beyond these five areas; this realm is what we call flavour, and much of this comes from our sense of smell.  For more information on how smell and taste work together to create flavour, see smell, taste and flavour.

Umami

Sweet, sour, salty and bitter are probably familiar to most people.  Umami, however, is perhaps less well-known.  It is a Japanese word that translates as ‘pleasant, savoury taste’.  We detect  umami via taste receptors that respond to glutamic acid and other amino acids.

Umami is present in a wide range of foods – anything that contains glutamates, including many fermented and aged foods.  Some examples include:

– Soy sauce
– Yeast extract (e.g. Marmite)
– Strong cheeses such as cheddar
– Mushrooms (particularly dried Shiitake mushrooms)
– Tinned anchovies
– Red meats such as beef – the more aged they are, the greater the levels of umami

There is some useful information on umami, including advice on how to utilise it when cooking, on the Molecular Recipes website.

The taste map myth

2000px-Taste_buds.svg

You might remember being shown a ‘taste map’ in a textbook at school like the one above, where the tongue is divided into regions, each one being responsible for detecting a particular taste: 1 is bitter, 2 is sour, 3 is salt and 4 is sweet.  This is another misconception about the sense of taste.

The taste map theory was found to be false in 1974 by a scientist called Virginia Collings.   Virginia reexamined a paper written in 1901 by German scientist called D.P. Hanig which had given rise to the tongue map theory.  She discovered that Hanig’s paper had been mistranslated and in fact had suggested that all tastes could be perceived on all parts of the tongue.

That said, we do experience stronger bitter tastes more towards the back of the mouth and sweet tastes at the front, so there is some spatial location of taste, just not in the way that the ‘taste map’ model suggests.

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