Put out your tongue. Look in the mirror and check its colour. Stroke it gently and check its surface feel. Keeping your sensory hardware in good condition is as important as learning your flavours and profiling your pints.

A pale pink, rough-looking muscular organ with a distinct response to the four major tastes is the target. Such an organ is essential in assessing beer. Less than this and you may be getting a one sided view of your beer.

Beer, of course, is nothing like as basic as purified chemicals but a complex mixture of up to 300 different components all targeted to stimulate different parts of our sensory organs. Similarly tongues are nothing like a simple muscle but a platform for a rich array of taste buds all aligned to sample your food and shout about its character and content.

This information contributes directly to the enjoyment of food. It also influences longer-term responses such as drinkability, habituation to a brand and even stimulation of the digestive system. Tingle the tongue and your customers may remain loyal to your beer.

Know your tongue

What then is on the tongue to cause such dedication? Look closely with a microscope or hand lens and you will see details of the many papillae across the surface. Each between 0.3 and 3 mm in diameter and rather like mushrooms among the leaves of a wood.

In fact one type of papillae, the fusiform, carries no taste buds but functions as a horny scale to carry food into the mouth. Cats show these more readily where they help tear flesh from bones or lap up liquids. Cows also use these to tear and hold grass. Human food is less demanding today but fusiform papillae are still present and contribute to the roughness of the tongue’s surface. Just try stroking your own – or a friend’s – to get the full feel.

Other papilli appear across the tongue and carry many of the 2,000 taste buds of the adult mouth. Fungiform papillae are the most common papillae generally at the front and sides of the tongue and carry many taste buds each. They resemble small red spots in the shape of button mushrooms.

Foliate papillae are a series of folds on the rear edges of the tongue. View these by pulling the tongue to one side and stretching the opposite corner of the mouth open. The foliate papillae appear redder than the surrounding tissue.

Valate papillae are larger, up to one cm across and quite prominent to the rear of the tongue. They are even surrounded by a moat containing salivary glands to lubricate the surface and remove tasting materials in a flow of saliva. Look for these as a line across the back of the tongue. As they are more sensitive to bitter tastes a large number of these receptors suggests you are more responsive to beer.

A standard view of the taste receptors is that they are zoned on the tongue with sweet response at the front, salt and sour at the side and bitter across the back.

Taste buds are the front end of the taste sensory detection system. This system is based on sensory cells which respond to taste molecules. Only a few molecules of a flavour can stimulate a response but how exactly is this achieved?

The common understanding is that the taste receptor cells have molecular receptors specific for each flavour molecule or type of taste. When these receptors are stimulated nerve impulses are generated and, if strong enough, are passed along nerve fibres to the brain. When routed to appropriate parts of the brain the impression of taste is generated. Unconscious effects are to stimulate appetite, induce nausea or worse according to the situation. Conscious effects are to initiate appreciation, discussion and, if positive, selection of the product.

This theory suggests that the taste cells respond to individual chemicals we then interpret as specific tastes. This may help explain how flavours are perceived in different parts of the tongue – one group of molecules with a particular structure stimulating sweet receptors, a different structure stimulating bitter receptors etc.

In fact, experiments with (low voltage) electrical currents on individual taste cells indicate that the actual response depends upon the intensity and duration of the stimulation. Given the right stimulation any cell may show all of the four tastes.

Fortunately, under normal conditions we react to food within fairly constant conditions and are familiar with the standard zoning noted earlier.

Besides the specific taste receptor cells other, trigeminal, nerves are also present in the mouth and respond directly with harsh and painful compounds such as capsicum from chillies as well as to heat and carbonation. These nerves conduct directly to the brain’s awareness area and can interact with the standard flavour response system.

Interpretation of the stimulation produced by the different receptors is evidently more complex than a direct response for each flavour and explains why food and drink can be so difficult to interpret – and beer so complex to describe.

In fact the four major tastes currently assigned to the tongue may be broadened to include astringent, electric, alkaline and metallic – the latter an important fault in some beers. Historically tastes were more extensive when initially classified by Linnaeus to include sharp, fatty, insipid, astringent, viscous aqueous and nauseous. Experiments to associate tastes with particular chemicals has reduced this list by removing those with aroma responses and others such as viscous and astringent which result from a physical effect on the tongue.

For beer sweetness and bitterness are the most dominant tastes but tasters must also be sensitive to acidity to detect spoilage by acetic and lactic acid bacteria.

Check your response

Sensitivity is an essential attribute of a taster. Indeed a few people are insensitive to basic flavours and should not be included in a tasting panel. If you are able to distinguish between basic samples of sugar, salt, lemon juice and coffee your response should be adequate, although the use of 0.2% sucrose, 0.02% salt, 0.07% citric acid and 0.07% caffeine is a more exact test used to recruit panel members.

One difficulty in comparing beers by tasting is the different sensitivities of taste panel members. Within the population the range of taste sensitivity can vary by 3 times for sweet, by 80 times for salt, by 200 for sour and by 200 for bitterness. With bitterness so important in beer flavour it is no wonder that our impression of a beer differs. The importance of taste training to standardise responses is thus particularly important when assessing beers.

Such variation in sensitivity may be a result of inherited ability, perhaps through the number of taste buds or their nerve connections. It is certainly known that super tasters exist with up to four hundred taste buds per square centimetre compared to the average 184. Sensitivity is also affected by illness and declines with age so consider carefully the protestations of the ageing brewer who claims that today’s beers are blander than the pinnacles of the past.

Know your flavours

While inherent sensitivity may set your tasting limits taste recognition is a more adjustable skill. Learning your flavours provides plenty of opportunity for homework.

Without practice the possibility of confusion between tastes is high and varies with the taste. For example, in one experiment, when a group of subjects were given a sweet sugar solution 10% believed it to be salty or sour. In the same trial only 80% identified salt as salty, only 63% identified hydrochloric acid as sour and a minority of 45% thought quinine to be bitter. Once again bitterness, the most dominant flavour of beer, is the least distinct flavour.

Such results suggest that confusion of taste may reign amongst drinkers. An additional possibility is that interactions between compounds may alter flavour impressions. Even small impurities can have significant effects.

For example when beet sugar is tasted at the same concentration as cane sugar it is commonly judged as less sweet. Chemical analysis of beet sugar indicates lower levels of calcium, sulphur and phosphate. Increasing the levels of calcium in beet sugar increases its perceived sweetness to that of cane sugar.

Beer is, of course, much more than a sugar solution with added bitterness. If a small amount of calcium can affect the impression of a sucrose solution imagine the effect of the liquor treatments of different breweries. No wonder it is so difficult to match beer character between breweries.

Interactions between tastes can depend upon concentration and by how much each compound is above the taste threshold. Generally the most concentrated taste in a mixture dominates but this can depend upon time and adaptation.

Timing is also important. Because tastes take different times to appear and disappear it is possible to taste two or more compounds sequentially in a mixture. For example sweetness is detected rapidly within a few seconds and declines equally fast. Bitterness can take minutes to appear and is characteristically the longest lasting taste, lingering for minutes. Taste a mixture and you should detect both. One following the other.

Continued exposure to a flavour can cause adaptation where the impression of the flavour declines after a period of time. Some compounds show cross adaptation for example where prolonged exposure to salt reduced bitterness perception. Yet another assault on the all important flavour feature of beer – and an important consequence of eating crisps with your pint. Interestingly bitterness does not show a reverse effect on salt perception.

Occasionally a more extreme interaction may occur. The compound miraculin found in the berries of the West African plant Synespalum dulcifum converts the taste of acids to sweet – an effect which may last up to three hours. Gymnemic acid from the leaves of the plant Gymnema sylvestre is more extreme and suppresses the ability to taste sweetness entirely. After exposure to gymnemic acid crystals of sugar taste like sand.

A more commonly experienced taste conversion is that promoted by monosodium glutamate, MSG. MSG in the presence of salt blocks the detection of saltiness and enhances other flavours.

Feel the burn

While specific chemical tastes are fundamental to the appreciation of food physical effects may be the most prominent in some cases and important contributors to a food’s character in others.

The burning sensation of capsaicinoid oils in chillies for example are common ingredients in many foods – and the occasional beer. Being tasteless and odourless their impact is directly on the exposed trigmenal nerves in the mouth. In extreme it can be an agonising distraction while you search for a glass of water. It certainly distracts from the subtlety of a beer.

Other unusual chemicals can have similar effects. Nitroglycerine, oddly enough, has a burning sensation but also a sweet taste. Its use in beers is, to date, untried.

Thiopropional sulfoxide found in onions and garlic induces tears due to the formation of sulphuric acid when dissolved in water. Neither onion or garlic beers are common but could have a potential for the melancholic.

The most common physical taste is that of tannins producing dryness and astringency. In chemical terms this is believed to arise from polyphenols coagulating proteins on the surface cells of the mouth. Changes to these proteins may shrink the cells and stimulate nearby nerves producing feelings of dryness and tightness. In some cases these may compliment the characteristics of beer. In others a harsh aftertaste may result and drive drinkers to water rather than the extra pint you were hoping. The use of tannin-free malts or careful processing to reduce tannins are possible means to minimise this reaction.

Taste the physical

Consideration of tannins leads into the topic of food texture. Most foods are critically dependent on their solid or semi-solid texture for success. A simple comparison of a warm and a cold chocolate bar can illustrate how texture affects taste.

With beer the major physical features are viscosity and carbonation. Of these viscosity has received less attention and then mostly to maximise filterability.

It now appears that viscosity may have an important effect on aftertaste and, possibly, on drinkability and is worthy of a more detailed study. Proteins, polysaccharides and polyphenols may all affect viscosity and may derive from many origins in brewing.

Carbonation is a more controllable ingredient and has a distinctive effect on beer flavour and quality. In general the higher the carbonation the higher the beer scores for quality. Naturally this effect has it limits, not least through the visual impression of over-foaming.

Flat beer is certainly poorly regarded for visual appeal against a bubbling pint. However, a beer need not be fizzy to taste outstanding as a multitude of cask ales demonstrate.

High carbonation may, arguably, suit paler, hoppier beers while dark, maltier beers are better served with more limited gas. It is certainly true that the higher the carbonation the greater the irritation of the trigeminal nerves and the more the mouth is distracted from tastes and aromas. This is not an excuse for increasing the carbonation on bad beers but a reason to more carefully balance the level of gas with the overall flavour character.

The use of mixed gases and the development of nitrogenated beers are prime developments in this area although other factors such as astringency from polyphenols, alcohol and proteins from malt also act on mouthfeel.

What is the future of the tongue in drinking? The promotion of beers causing limited impact and offence to the tongue suggests a concern to minimise flavour impact in preference to the refreshment and stimulation provided by chilled and highly carbonated beverages.

Is there a future for a fuller stimulation or is it a declining market? Even the level of bitterness in premium cask UK beers has declined in the last 8 years. Perhaps we need to assess the relationship between stimulation and satisfaction?

Furthermore if health concerns lead to drinkers limiting the quantity of their alcoholic intake we may need to maximise stimulation and provide more opportunity for the tongue’s other use – the mechanics of discussion. Put out your tongue, taste beer, talk beer.


Written by Dr Keith Thomas
Brewlab Director

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