Tuesday, 28 October 2014

Personal taste

In recent posts, I have written about the environmental factors that influence how we perceive food and drink.  To complete this mini-strand, I offer a few words on the genetics of taste perception.

Back in 1931, a chemist called Arthur Fox was carelessly working with a powder called phenylthiocarbamide (TCP). His colleague complained that some of the airborne powder tasted bitter, but Fox could not taste anything. Studies to date have confirmed that around 75% of people can taste TCP and 25% cannot. With increasing knowledge of genetics, this ratio strongly suggested that a single dominant gene was involved in TCP perception; though the fact that people vary in their sensitivity to it suggests that other factors are also involved. In 2003, geneticists identified the gene – TAS2R38 – coding for the TCP receptors.

TCP does not occur naturally, so what is the significance of this? The answer was once life or death, of course. The TCP receptors are just part of the structures on the tongue that detect bitter substances. There are now around 30 genes linked to such bitter taste receptors. Your ability to taste TCP is positively correlated with your ability to taste other bitter substances, most significantly toxic compounds in plants that you might want to try eating.

I was reminded of this at Green Man this summer. One of the University Science Department stands in the Einstein’s Garden area of the festival was conducting simple genetic test, including the one for TCP perception.  As on previous occasions, this confirmed that I can taste TCP. Though this leaves a bitter taste in the mouth, it is a good thing (and they did supply sweets afterwards). It means I have a better chance of detecting bitter toxins in my food than people who cannot taste it, or it would if we all still lived in the age before supermarkets.

The genetic component for the perception of the other four basic tastes is thought to be less strong, though recent research has revealed that the perception of sweetness is partly inherited. This research is being done with a view to understanding obesity. Genetics may have little bearing on how we perceive salty and sour, while less is known about unami generally.

There are a number of technical terms to describe medically-related conditions involving taste perception, but these are more linked to environmental factors, particularly the onset of certain diseases, than genetic factors. For example, people can have ageusia (complete loss of taste), hypogeusia (partial loss of taste), dysgeusia (distorted sense of taste) and hypergeusia (abnormally heightened sense of taste). While ill, I have experienced mild versions of a couple of these and it certainly makes you appreciate your food when you recover.

One of the many environmental factors influencing how we perceive taste is aging, with older people often having reduced sensitivity to salty or bitter tastes. Acquired tastes are preferences that develop over time. These can override any genetically determined aversion to bitter or unusual tastes. Coffee, Marmite, broccoli, goat’s cheese and Brains Bitter, for example, are acquired tastes. It all goes to show that taste can be a very personal thing.

See also:
Crossmodal sensory perception
http://sfnottingham.blogspot.co.uk/2014/09/crossmodal-sensory-perception.html

Pete Brown on beer and music
http://sfnottingham.blogspot.co.uk/2014/08/green-man-2014-welsh-beer.html

Some archived posts you may be interested in:
Genetics at the National Botanic Gardens of Wales
http://sfnottingham.blogspot.co.uk/2011/03/barcode-wales-science-at-national.html

Apples
http://sfnottingham.blogspot.co.uk/2011/03/apples.html

Raw Vegan Rock and Roll
http://sfnottingham.blogspot.co.uk/2012/04/raw-vegan-rock-and-roll-jonsi-and-alexs.html

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