Science Interviews


Fri, 8th Aug 2014

Making sense of taste

Barry Smith, University of London

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Our perception of flavour isn't just influenced by our taste buds. Smell, touch and Red Delicious applessound all have a big role to play when we decide how much we might like or dislike a certain dish. Professor Barry Smith gave Kat Arney a small taste of how this can work...

Barry -   So, I'm going to show you something a little bit strange.  I'm opening this packet of sichuan pepper corns.  Iíll give you a little one of these.  What I want you to do is just chew on that.  Thatís a very strong perfume.  If you smell, itís got aÖ

Kat -   Spicy, yeah.

Barry -   Spicy, butÖ

Kat -   Peppery kind of... Very aromatic.

Barry -   Very aromatic, very floral.  So, pop that in and start chewing.  Iíll tell you a little bit about it.  So, here is another ingredient that we can add to the range of sensations.  Itís quite strong but does something start to happen to you?

Kat -   Tingling.  Yeah, really tingly on my tongue, just likeÖ

Barry -   Electricity?

Kat -   Yeah, like a really kind of Ė not quite the curry hot, but yeah, like something bad is going on.

Barry -   Okay, so that tingling sensation.

Kat -   I'm not sure I like this you know.

Barry -   No, okay.  What's happening is that the active compound in Sichuan pepper is called sanshool and it stimulates the mechano receptors.  Itís actually making your tongue vibrate at 50 hertz.

Kat -   [laughing].  My tongue is vibrating.  Certainly, my mouth is watering.

Barry -   Your mouth is watering, yes.  Thatís the other effect.  When that happens, somehow rather, your saliva glands just run and run and run.  You may need some more water to deal with that.

Kat -   This is not exactly pleasant, I have to say.

Barry -   No.  I've given you a tiny pepper corn and you donít need to have too much of that to have the effect.  But itís interesting that thatís vibration.  So, notice that what's actually giving you that sensation, some people say, ďOh, is it burning?Ē  No, itís not burning.  It is tingling, but its vibration, itís pure vibration.  If you touch it, it can actually stop if you actually got enough fingers on your tongue to hold it, you can still it for a little while.  We can do this better on the lips.  When people have a little bit of it on their lips, they touch the lip, you can still the vibration.

Kat -   Oh yeah.

Barry -   Right, so thatís justÖ

Kat -   Still dribbling after a while there.

Barry -   You're still dribbling, I know.  I may have to talk until you recover.  But this is again just showing you that youíve got vibration.  Youíve got touch, youíve got the stinging, burning, tingling, of trigeminal sensation.  Youíve also got smell.  Youíve got taste.  So, a huge number of senses are coming together and yet, very often, when we get a complex dish, you think, itís just one thing Ė the flavour.  So, the brain is putting together a tremendous amount of information and computing it to provide a unified percept, a unified experience of that flavour of something even though we now know itís a very complex fusion of many, many different senses.

Kat -   So, if we think that the taste of something is made up of this very, very complex interplay of our senses, what can we do then to fool our senses or to make our food maybe more exciting or interesting?

Barry -   Yes, this is one of the things that chefs are obviously aware of, is that now they know that the pallet to work on is including not just taste and smell from the food, not just the texture of the food, which is important, but there are other ingredients that they can use including for example sound.  So, one of the strange things is that sound has an impact on how you taste things, on the flavour of things.  But there's also another dimension of tasting we haven't talked about and that is the fact that we get a temporal dynamic when weíre tasting.  Tasting is not a single experience.  Tasting is a sequence of experiences of say, a wine entering the mouth and traveling across the tongue, and then swallowing.  When you swallow, thatís when you pulse lots of odours up into the epithelium and you get that big hit of flavour.  So, if the tempo and the pace of something traveling across the tongue were to match the tempo of a piece of music then we know the brain is on the lookout for any matches and it probably thinks, ďOh, these are simultaneous or synchronous.  Pay attention to it.Ē

Kat -   So maybe if you were in a wine bar and you're thinking, ďYeah, this wine is really niceĒ and then you try it at home, it doesnít taste the same.  Could it be because of the atmosphere, maybe the music thatís playing there is affecting your perception of the taste?

Barry -   Absolutely, it could be and I always say to people when they choose a really nice bottle of wine in a restaurant and they're looking forward to it, then they have to suffer whatever the duty manager has put on the CD and it may not work.  So, donít like the wine, change the music.  Maybe the music will actually enhance the wine, help you to pick things out.  So, I'm going to try and give you another indication of how sound plays a part in tasting.  Here, I'm going to see whether or not sounds are going to give you clues about whether something is sweet or sour or bitter.  So, I'm going to play you three noises.  Iíll play them first and I want you to say which oneís sweet, which oneís sour, which oneís bitter, okay?

Kat -   Okay.

Barry -   So, here we go.  Hereís the first soundÖ

[Piano music]

Kat -   That does sound okay.  I think thatís sweet.  Iíll go sweet with that.

Barry -   You're right.  Thatís sweet.  Letís try this oneÖ..sweet, sour or bitterÖ

[high piano music]

Kat -   I think thatís kind of sour, sort of acid drops.

Barry -   Thatís right.  Thatís exactly what it is.  And so, the last one must be bitter.  Let me just play that for you.  Hereís the last oneÖ.

[deep piano music]

Kat -   Yeah, I'll will go with that.

Barry::  So, I thought that was great when you said Ďacid dropsí because you can see why immediately the sourness, that sort of percussiveness, quick high percussive.  You might think of it as being even sharp.  Notice that when we say sharp, sharp is a feel.  So, see how easy it is for our language to do this cross model comparison.  You're moving from taste to touch.  You're saying, ďIt tastes, lemon juice, tastes sharpĒ and of course, sharpís a feel.  But it gives you that feeling then when you're listening to a sound of the percussive ting, ting, ting, ting as opposed to the slower, softer tones of sweetness.  Of course, the acidity receptors on the tongue, they will fire up more quickly and therefore, you'll have that very fast reaction whereas the slow onset of building up to full intensity with the sweetness receptors is different.  But that was an example of how one trial learning without any previous experience, you could sort those sounds quite naturally into sweet, sour and bitter.  It shows you that the brain is already associatively set up to compare sounds to tastes.


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