Can you taste without smell?

Biochemist Sarah Madden revealed why your nose knows best when it comes to flavour...

Sarah - Someone wanted to know if you could taste food without smelling it. The thing is our tongues have five basic tastes so we have sweet, sour, salty, bitter and umami, but taste is kind of different from flavour. Taste is just when you put food on you mouth and you have a chemical reaction and you have a couple of those sensations that I just talked about. But smell also impacts on flavour so this is what the experiment is about. You can’t have complete flavour without smell so that’s what my experiment will hopefully demonstrate to these willing participants.                                 

Chris - This is a question we got from someone called Lauren who wanted to know how we disentangle the two effects - the smell and the taste. What have you got in mind; what do you want us to do?

Sarah - I have a jelly sweet with me.

Chris - One for all three of us to share or do we get one each?

Sarah - I have some jelly sweets.

Chris - Do you want to dish them out then?

Sarah - I can dish them out.

Chris - Because David’s looking hungry…

Sarah - There you go David.

David - I spotted these when these arrived. I’ve been looking forward...

Chris - I’d love one yes please.

Sarah - The idea is to split it into two. We want to be proper scientists and have a controlled experiment.

Chris - Okay. I’ve got two halves.

Sarah - For the first half we need to make sure we hold our noses very tightly so we can’t smell. I want you to put in your mouths and try and eat it.

Chris - I’m holding my nose and I’m going to eat the jelly sweet.

David - What’s umami?

Sarah - It’s almost a meaty flavour. You’ve heard of MSG as well - it’s glutamate or something that you find in meat so it’s that kind of almost sort of savoury, meaty flavour that they have just started thinking about, and scientists have only recently discovered that one.

Chris - So let’s ask Gareth chomping away over there while holding your nose. Could you taste your jelly sweet while you were holding your nose?

Gareth - No, but I tasted it as soon as I let go of my nose.

Sarah - Yeah, that’s really interesting.

David - Exactly the same. I really was gripping my mouth quite tightly and I could not taste that. I released my nose, as Gareth spoke, and I was flooded with orange.

Chris - Flooded with flavour. So Sarah - explain…

Sarah - That’s really good that you guys noticed that. The point is that when we’re holding our nose we can’t smell, all we have is the taste and not the flavour, so we just taste the sweet sensation is all we experience.  But, as we take our hands off our noses then suddenly we get the smell and hence the flavour. I’ve given you the second half in case you didn’t fully taste it as a little treat and reward...

Chris - I’m into that now. I’m now eating that.

Sarah - … for participating in the little experiment.

Chris - I didn’t take much encouragement. So the point is if you can’t get the air flow flowing down your nose because your holding it, it can’t carry those  flavours being volatilised boiled off by the warmth of your tongue up to where the olfaction, the smelling bit that happens in the back of the nose. As a result, you can’t ‘taste’ anything?

Sarah - Yes, exactly. It gives you an understanding of those people who can’t smell, like people with anosmia it’s called. So you can imagine what their experience of food must be like. It must be very difficult.

Chris - I used this trick when I was little because I hated brussel sprouts. I really like them now but I used to hate them and so I found the five year old me discovered if I held my nose I could eat brussel sprouts with impunity.  Because most of that strong flavour is very sulphurous compounds that then boil up to the back of your nose and you smell and call that taste.

Sarah - You’re destined to be a scientist weren’t you?

Chris - I clearly was. David?

David - So when we smell as we’re tasting, is it because we’re breathing out through our nose and drawing air from our mouth into our nose internally, or is our nose smelling what we’re breathing out?

Sarah - I would hypothesis - a combination. But it’s important to also emphasise that flavour is also a combination of sight and texture and heat. So it’s all things coming together.

Chris - Your brain is integrating all of these things together so that what we call “taste” is actually a mixed bunch of senses isn’t it I suppose?

Sarah - Mmm.

Chris - Thank you very much Sarah. So there you go, a little trick everybody, if there’s something very unappetising on your dinner plate, the way round this is hold your nose and then you won’t taste it.