Taste has a number of functions:
- Taste signals the nutritional qualities of the food we are about to eat.
- Taste helps us detect toxins in our foods to keep us safe.
- Taste links our external environment to our internal needs (hunger and thirst).
- Taste prepares our bodies to take in (ingest) food, encouraging eating through the satisfaction of need and the pleasure it gives.
How taste works
Taste is one of the main functions of the tongue. Look in the mirror and poke out your tongue as far as you can. You should see little bumps clustered on the sides and tip. At the back are larger flattened peg-like structures (like small button mushrooms).
These bumps and pegs are papillae. There are 4 main types:
- Circumvallate papillae are defined by the ridge of tissue that runs around (circumference) the edge of each one. They are arranged in a V formation pointing towards the throat, and there are 9–14 of these peg-like structures present. These papillae have a large number of taste buds arranged in tiers in troughs on their inner walls.
- Fungiform papillae are shaped like button mushrooms and raised slightly. They are scattered over the tongue surface concentrated at the tip and sides. They have taste buds embedded in their upper surface.
- Filiform papillae are conical-shaped structures found in large numbers over many parts of the tongue. They don’t contain taste buds so have no taste function. Their main job is to act as abrasive structures giving the tongue a cleaning, rasping action helping it grip food. To assist with this process, brush-like structures or secondary papillae project from the tip of each papilla. These structures also give the tongue a velvety or furry appearance.
- Foliate papillae are clustered on each side of the tongue in the transverse folds found there. Taste buds are found in these folds.
Each taste bud contains 30–50 taste receptor cells in a bundle like a bunch of bananas. Each cell has tiny hair-like structures, called microvilli, sticking up towards the taste bud surface forming a taste pore.
Taste molecules of food touch the taste pores and bind to the microvilli. These ‘tastes’ are changed into another type of message, which moves along the sensory nerves via chemical and electrical pathways to the brain, registering what you are tasting.
How we taste
Scientists once believed that the tongue was divided into strictly defined sections, each responsible for a particular taste.
This is now known not to be true. There are small differences in taste sensitivity in certain areas of the tongue. In general taste buds located in all areas of the tongue can distinguish all taste types.We now know that there are 2 main taste areas and that you can taste all taste compounds everywhere on your tongue, as long as you stimulate taste receptor cells:
- Gustation has the following taste areas – hedonic or appetitive (salty, sweet, umami or savoury), aversive (bitter or sour), heat (detected by vanilloid receptors reacting to the capsaicin in chilli peppers) and energy (found in the fatty acids of oils and fats).
- Orosensation or trigeminal sensation involves touch, temperature, pain and pressure.
There is a difference in taste sensitivity among humans:
- About 25% of the population are ‘supertasters’ – they have more fungiform papillae (and therefore taste buds) than others and they are very sensitive to the chemical PROP (6-n-propylthiouracil) and dislike bitter or ‘hot’ tasting foods. More women than men belong to this group
- ‘Normal’ tasters occupy about 50% of the population.
- The remaining 25% are ‘non-tasters’ – they are unable to taste PROP and often like bitter, strong, high sugar and salty foods.
These differences are inherited through the number of taste buds on the tongue, with numbers of taste buds declining with age.
Nature of science
As our science knowledge increases in a certain area, theories that seemed to explain observations in the past may need to be expanded, revised or even discarded in order to take into account recent scientific discoveries.
We can also adapt quickly to a taste. An example of this is the first taste of a drink that may seem sweeter than the next taste, because you adapt to the level of sweetness.
Learn how sensory scientists at Plant & Food Research conduct sensory trials with apples.
Try these activities with your students
Find out more about supertasters on the BBC website.
Research findings from the Monell Center released in April 2019 reveal that smell receptors have been discovered on the human tongue, implying that we might be able to use them to smell too. This could lead to new research approaches into ways to modify food flavour.