Touch. The Neglected Sense.
Better Tourism, Not Bigger
November 14, 2023
Focus: Product Development Directorate (MTA)
November 17, 2023As Chefs, cooks and foodies we all know the importance of the senses while we are eating.
Taste, what we sense on the tongue indicates the presence of non-volatile compounds such as salty, sweet, bitter, sour and umami; the nasal receptors in our nose catch volatile compounds, those distinctive notes that give an ingredient its flavour.
Then there’s sight, the all important sense, everyone states the same “we first eat with our eyes”, and it’s true sight plays an important role in how we eat and perceive the food in front of us. These three senses combined are estimated to contribute around 95% of our total flavour perception. But what about our other senses? Are they not as important?
Let’s start with touch, also known as the somatosensory system. We have ‘touch’ receptors all over our body, including the inside of our mouths and noses. These receptors are responsible for picking up tactile stimuli such as temperature, pain, texture and so on. These receptors then pass messages to the somatosensory cortex and there the information gets deciphered, giving us our sense of touch or feel, if you will.
Now with regards to eating and drinking, we can split these up into two categories, internal and external stimuli. Internal stimuli are the most commonly talked about when referring to food, and simply put they are stimuli we feel in the mouth and nose during consumption.
Thermal stimuli indicate when foods and drinks are hot or cold. For example, we all love a steamy bowl of soup on a cold winter's day or an ice-cream in summer, but there is far more to it than that. Ice-cold foods cause a delay in the perception of all the tastes due to the brain being preoccupied by the pain brought by the intense cold, as an example. Cold temperatures also decrease the perception of almost all the tastes due to the receptors on the tongue closing up, while at room and body temperature the body opens its receptors and all the tastes peak, especially bitterness.
Now thermo-sensory perception creates a sort of U-shape curve, and bitterness, as an example, is dulled by heat, that’s why bitter beverages like coffee are usually taken while still very hot. Leaving that coffee to cool to room temperature it’s disgusting, and this is just how temperature affects taste. Two temperatures on the same plate however will arouse curiosity in the brain and increase its liking, think molten chocolate fondant with freezing vanilla ice-cream. Oh… and on a fun little note, did you know that our mouths cannot tell the difference between chemical and thermal stimuli?
These effects are known as chemosensory perception, so the pain we get from capsaicin or piperine, the chemical compounds that give chili and pepper, respectively, their burning sensation in the mouth is deciphered in the brain in the same way as having your mouth burnt on some molten cheese. Menthol, the cooling alcoholic compound found naturally on mint is deciphered as a cooling effect, same as drinking an ice-cold drink, as far as the brain is concerned.
Spilanthol a chemical in Sichuan blossoms, numbs the mouth completely and causes excessive drooling, and that burn you get from wasabi or mustard, doesn’t actually cause pain in the mouth, they cause the pain receptors in the nose to be activated, thanks to a family of compounds called isothiocyanates. Each person has different sensory thresholds to these stimuli, meaning that the heat from a very hot chili pepper might be enjoyable to some and an awful experience to another. Having said that both thermal and chemical stimuli cause an emotion that fundamentally has a real effect on the dining experience.
Then comes my personal favourite part of internal somatosensory perception, sapictive tastes, i.e. a taste that is not actually there but we perceive it as such just because our brain deems it so. Take sparkling water as an example, it tastes sour, but it isn’t acidic, that’s because the texture given by the carbonation makes our mind believe that the water is acidic when it really isn’t. This is also why a fresh carbonated soft drink tastes good, but once it goes flat it becomes far too sweet - plus sweetness and acidity tend to counter each other. Same with pureées, take a smooth puree of whatever ingredient you like, it will give you a sapictive buttery flavour that isn’t there.
Textures have non-sapictive roles also in changing flavour, crunchy and crispy foods dull the perception of salt. Even a foods’ density affects the overall flavour, a thick Greek yoghurt with the same amount of strawberries inside of it as a regular yoghurt, will taste less strawberry like, and a denser sausage will be perceived as being less salty than its looser counterpart, even though there’s the same amount of salt in both. And trust me when I say I’m barely even scratching the surface here.
Then you have external tactile stimuli, which are almost always neglected, but whose effects have been known to science and dining for over a century, and yes before we begin; the clothes you wear, the texture of the tablecloth and even the weight of things all affect flavour! But I’ll keep it short.
A fun experiment I like to show my students and something easy you can do at home; try eating natural yoghurt while rubbing sandpaper, you’ll find the yoghurt to be disgustingly sour. Simply put our brain associates textures to tastes, these are known as synaesthetic effects, rough textures often resulting in the increase of sour tastes, while silky textures result in the increase of butteriness. So, if you’re wearing jeans while eating an orange, you’re more likely to find that orange slightly sour than if you were wearing a silk bathrobe.
So, while dining out the clothes your clients wear definitely affect flavour and in some cases this is why dress codes are so important. These rules also apply to the texture of cutlery, rough cutlery, say with wooden handles accentuating acidity, but weirdly enough have been proven to boost the overall likeness of meat. In fact meat served on a rustic wooden stick tastes better than that on a plate, obviously meat of the same quality cooked to the same degree… and while on the subject of cutlery, the heavier the better.
Heavier cutlery has been proven to increase the value and flavour of the food they are eaten with. Same goes with glassware, the heavier the glass the better the flavour, with the exception of wine, thinner, finer wine glasses have been proven to promote better flavours in the wine, but give a fine, light glass for some sparkling and it will probably feel almost flat, unless the glass has a rough texture which will then increase the perception of carbonation. It gets a little bit complicated; I know.
Consider this, at a restaurant one would rather use a cloth napkin than a paper one, its seen as higher class and it is, but strangely enough, blindfolded tests show that it’s the weight of the object that makes it seem better rather than the perceived material being cheaper (which honestly, can be the case also). All this said, we also need to take into account trends, designs and consumer psychology, all of which have a role to play in the perception of flavour.
We only scratched the surface of tactile sensation and its effects on flavour in this article, but hopefully one can see its importance and how one of our forgotten senses, in relation to food, affects the overall flavour of everything we consume. Afterall dining out should be a feast for all the senses no matter how small of a percentage they provide to a gastronomical experience.
Keith Abela
Keith Abela is a forager, product developer and local food consultant. Who spends all of his time researching the delicious, rare and unique ingredients Maltese nature has to offer. He has a particular interest in multisensory flavour perception and all things fungus.
Click here to see Horeca Issue 13 online
Let’s start with touch, also known as the somatosensory system. We have ‘touch’ receptors all over our body, including the inside of our mouths and noses. These receptors are responsible for picking up tactile stimuli such as temperature, pain, texture and so on. These receptors then pass messages to the somatosensory cortex and there the information gets deciphered, giving us our sense of touch or feel, if you will.
Now with regards to eating and drinking, we can split these up into two categories, internal and external stimuli. Internal stimuli are the most commonly talked about when referring to food, and simply put they are stimuli we feel in the mouth and nose during consumption.
Thermal stimuli indicate when foods and drinks are hot or cold. For example, we all love a steamy bowl of soup on a cold winter's day or an ice-cream in summer, but there is far more to it than that. Ice-cold foods cause a delay in the perception of all the tastes due to the brain being preoccupied by the pain brought by the intense cold, as an example. Cold temperatures also decrease the perception of almost all the tastes due to the receptors on the tongue closing up, while at room and body temperature the body opens its receptors and all the tastes peak, especially bitterness.
Now thermo-sensory perception creates a sort of U-shape curve, and bitterness, as an example, is dulled by heat, that’s why bitter beverages like coffee are usually taken while still very hot. Leaving that coffee to cool to room temperature it’s disgusting, and this is just how temperature affects taste. Two temperatures on the same plate however will arouse curiosity in the brain and increase its liking, think molten chocolate fondant with freezing vanilla ice-cream. Oh… and on a fun little note, did you know that our mouths cannot tell the difference between chemical and thermal stimuli?
These effects are known as chemosensory perception, so the pain we get from capsaicin or piperine, the chemical compounds that give chili and pepper, respectively, their burning sensation in the mouth is deciphered in the brain in the same way as having your mouth burnt on some molten cheese. Menthol, the cooling alcoholic compound found naturally on mint is deciphered as a cooling effect, same as drinking an ice-cold drink, as far as the brain is concerned.
Spilanthol a chemical in Sichuan blossoms, numbs the mouth completely and causes excessive drooling, and that burn you get from wasabi or mustard, doesn’t actually cause pain in the mouth, they cause the pain receptors in the nose to be activated, thanks to a family of compounds called isothiocyanates. Each person has different sensory thresholds to these stimuli, meaning that the heat from a very hot chili pepper might be enjoyable to some and an awful experience to another. Having said that both thermal and chemical stimuli cause an emotion that fundamentally has a real effect on the dining experience.
Then comes my personal favourite part of internal somatosensory perception, sapictive tastes, i.e. a taste that is not actually there but we perceive it as such just because our brain deems it so. Take sparkling water as an example, it tastes sour, but it isn’t acidic, that’s because the texture given by the carbonation makes our mind believe that the water is acidic when it really isn’t. This is also why a fresh carbonated soft drink tastes good, but once it goes flat it becomes far too sweet - plus sweetness and acidity tend to counter each other. Same with pureées, take a smooth puree of whatever ingredient you like, it will give you a sapictive buttery flavour that isn’t there.
Textures have non-sapictive roles also in changing flavour, crunchy and crispy foods dull the perception of salt. Even a foods’ density affects the overall flavour, a thick Greek yoghurt with the same amount of strawberries inside of it as a regular yoghurt, will taste less strawberry like, and a denser sausage will be perceived as being less salty than its looser counterpart, even though there’s the same amount of salt in both. And trust me when I say I’m barely even scratching the surface here.
Then you have external tactile stimuli, which are almost always neglected, but whose effects have been known to science and dining for over a century, and yes before we begin; the clothes you wear, the texture of the tablecloth and even the weight of things all affect flavour! But I’ll keep it short.
A fun experiment I like to show my students and something easy you can do at home; try eating natural yoghurt while rubbing sandpaper, you’ll find the yoghurt to be disgustingly sour. Simply put our brain associates textures to tastes, these are known as synaesthetic effects, rough textures often resulting in the increase of sour tastes, while silky textures result in the increase of butteriness. So, if you’re wearing jeans while eating an orange, you’re more likely to find that orange slightly sour than if you were wearing a silk bathrobe.
So, while dining out the clothes your clients wear definitely affect flavour and in some cases this is why dress codes are so important. These rules also apply to the texture of cutlery, rough cutlery, say with wooden handles accentuating acidity, but weirdly enough have been proven to boost the overall likeness of meat. In fact meat served on a rustic wooden stick tastes better than that on a plate, obviously meat of the same quality cooked to the same degree… and while on the subject of cutlery, the heavier the better.
Heavier cutlery has been proven to increase the value and flavour of the food they are eaten with. Same goes with glassware, the heavier the glass the better the flavour, with the exception of wine, thinner, finer wine glasses have been proven to promote better flavours in the wine, but give a fine, light glass for some sparkling and it will probably feel almost flat, unless the glass has a rough texture which will then increase the perception of carbonation. It gets a little bit complicated; I know.
Consider this, at a restaurant one would rather use a cloth napkin than a paper one, its seen as higher class and it is, but strangely enough, blindfolded tests show that it’s the weight of the object that makes it seem better rather than the perceived material being cheaper (which honestly, can be the case also). All this said, we also need to take into account trends, designs and consumer psychology, all of which have a role to play in the perception of flavour.
We only scratched the surface of tactile sensation and its effects on flavour in this article, but hopefully one can see its importance and how one of our forgotten senses, in relation to food, affects the overall flavour of everything we consume. Afterall dining out should be a feast for all the senses no matter how small of a percentage they provide to a gastronomical experience.
Keith Abela
Keith Abela is a forager, product developer and local food consultant. Who spends all of his time researching the delicious, rare and unique ingredients Maltese nature has to offer. He has a particular interest in multisensory flavour perception and all things fungus.
Click here to see Horeca Issue 13 online
