Paul Merrett: Hi, I'm Paul Merrett, chef and presenter of the BBC Open University TV series Ever Wondered About Food? - and that's what I've spent a vast amount of my life doing, wondering about food - and, luckily, when I'm wondering I've often got David Shuker of the Open University with me, who's the man behind all the science on the programme.
David, one of the things that I've really noticed as I've got into food is that it's not just fuel for the body; it can be a little bit more than that. I remember one of the people I worked for was a very wealthy restaurateur who often took me to France, to Paris, to some of the finest Michelin restaurants, and the first thing he'd do, when he'd got his plate of food put in front of him, was drop his head to the table and take a great big sniff of it, and that would be the start of his eating experience.
And although at the time I sort of looked away in a slightly embarrassed state, I do know what he means - there's something great about actually smelling the food and looking at the food before you actually dive into it. Is there a science going on there? Is our nose actually all part of the eating experience?
David Shuker: I think it is. I think it's one of those things. It's to do with the appearance of food, the colour of food, the taste of it, of course. But actually it's interesting you mention that story, because almost the first thing, you see, after you've seen your food is to smell it before you taste it. And of course, I suppose, in thinking about it, as that dish left the kitchen, the chef who prepared it - his last encounter was that last taste or the last smell of it. So, to do justice to it, you might imagine well the best thing to do is to just savour it for the moment.
Food is going to give off all sorts of smells. The receptors in our nose are very sensitive to all kinds of subtle molecules and, depending on the dish, we get a different signal. And as well as that, of course, it's also - rather than just beginning to eat straightaway - just looking at the food and thinking well, why is this nice? …smells nice? …looks superb if it's in a nice restaurant?
Paul Merrett: Yes, and I think also, if you think of the high street, I seldom walk past the coffee shop, where they're grinding coffee, without thinking "well actually it would be quite nice to have a coffee." And of course supermarkets have worked this out by pumping out that sort of fresh baked bread smell and you just instantly feel hungry. And on the programme we did a great episode about nuts, and nuts have got a very distinctive smell, whether cooking or just, shelled nuts obviously, just the smell of pine nuts and the smell of almonds. Chemically, or molecularly, what's in there that's giving off that fantastic aroma?
David Shuker: Well, it's very interesting. In the case of almonds, for example, there is one molecule, it's called benzaldehyde, which is so distinctive that if I were to take you into my laboratory and open a bottle of benzaldehyde - because you can just buy pure benzaldehyde - when I pop that under your nose and say just take a whiff of this, Paul, you'd say, "mm that's almonds." Now it's not a bottle of almonds, it's a bottle of benzaldehyde, and it turns out that that is the molecule that gives almonds a distinctive flavour. And pine nuts contain a number of molecules which are very distinctive to pine, and if you were to smell the pure molecules you'd say "pine!" and there are a lot of ones like this.
I once went into a flavour laboratory, and round this laboratory were lots of little bottles, and they all had pure chemicals in them. And the chemist who took me in there said, "Now, smell this," and I smelt the liquid, and I said, "Mm, orange!" and he said, "Fine." And he took the next one out, and he said, "Smell this then". "Ah that's grapefruit!", and put it down. And it turned out that they were virtually identical molecules, but ever so subtly different, and our nose can distinguish that subtle difference.
Paul Merrett: That is incredible. In a sort of reverse of that, I've done tasting days in schools, and one of the things I do is I take in five or six different flavoured yoghurts, and I sit with the kids - they don't know what the flavours are - and we get them to pinch their nose quite hard and eat the yoghurts. And without the nose, very few of them pick out the flavour that they're being fed. And as soon as you release it, they'll say "Oh yes, that's blackberry," or "That's strawberry." And it's really interesting, without even thinking about it, how much of a part our nose is playing in the eating experience isn't it?
David Shuker: Yes, absolutely.
Paul Merrett: It's got a big part. Now "nuts" is a huge subject because there are so many of them, and one of the first things we discovered when we actually flooded the table full of nuts is that half of them weren't nuts, and it all got very technical, and we ended up phoning Kew Gardens and botanists all over the world saying is a hazelnut a nut or is it a fleshy something or other? But to the cook they were all nuts. And they're really interesting to cook with because they do give a fantastic flavour, and they give a smell, as we've just said, but they're also really interesting I think as a texture. I think a fruit cake with nuts is - I don't think that there's a texture similar to coming across a nut in food. I don't know whether you agree with that, but I think they really give quite a distinctive element to a dish.
David Shuker: I think you're right. I think the first thing is that sort of quintessential nuttiness, that sort of nutty flavour, which often, of course, that only develops when the nuts are roasted. So you need to roast them, and that in itself is interesting, and I know there are whole projects devoted to try and reconstruct sort of roasted nut flavours because it would be quite nice to have those as an artificial flavour - it turns out to be extremely difficult because it's very delicate the way it goes.
But when it comes to the texture, I mean a few years ago I went to a great scientific conference in Hawaii and I came across Macadamia nuts, which are grown… and what about that for a consistency because they're creamy - you bite through a Macadamia nut and it's the most creamy soft thing, and it's unique to that nut. And I'm not actually a great fan of nuts myself, I find the nuttiness a bit too much, but I know there are nuts that are absolutely marvellous; I mean pistachio nuts I love, and they've got quite a nice taste and consistency too.
So yes, there's a whole range, and I can understand from a chef's point of view, you've got this whole sort of palette of flavours and textures to deal with.
Paul Merrett: I think they're very interesting. I use them more at work than at home because my wife is allergic to nuts - and there are a lot of people with a nut allergy. We've got two young children, we were advised to introduce them very carefully to nuts and just sort of see how they responded, and they've been absolutely fine; there's been no reaction whatsoever. Why is it such a common allergy?
David Shuker: It's not at all clear why it's such a common allergy. I mean, I think we understand why nuts cause an allergy, and that is that some of the proteins in nuts are recognised by the body as something foreign. So if babies and young children are exposed to those proteins then effectively their immune system sets up a response, which means if they encounter them later, they get this, sort of, what's called the anaphylactic response, which can be quite serious in people, so you need to know about it. It's not at all clear whether it's because nuts are being used so widely in all sorts of foods. I mean whether, for example, baby foods might contain nut proteins, almost inadvertently, although I think manufacturers that use them are so aware now that it's probably going to be a problem that may end up being resolved, I don't know, but certainly we know it's the proteins in the nuts. And it's not a dissimilar problem to the problem that some people have with milk, because it's milk proteins that cause that.
Paul Merrett: Which is strange, because you thought as an animal, nuts must have played a part in our foraging and gathering, and they must have been something that we came across and ate.
David Shuker: We did, but remember of course that nuts, we have - as we've discussed - a large range of nuts available, and some of these come from quite distant countries. I mean you think for example that peanuts come from East Africa, brazil nuts come from Brazil, and so actually it's only in relatively recent times, probably less than the last hundred years, that we've been exposed to such a wide range, and so that might, I think, explain… these are many nuts that have only come onto our dietary scene relatively recently.
Paul Merrett: But, paradoxically, they're also very good for you, because they contain some very healthy oils.
David Shuker: They're good for you - very healthy oils, and certainly the protein content; they're a very good source of protein. So basically, yes, they're good foods. And obviously, again, going back to sort of stories of hunter gathering, I mean, if you lived in a part of the world where wild nuts grew, then clearly they were a very good source of food.
Paul Merrett: Well, I grew up in Zanzibar, which is a little East African island, and the island is absolutely covered in coconut trees, and so I've eaten my fair share of coconuts. And I think, as a cooking stock, coconut milk is a fantastic flavour, because it brings something to a dish that you really can't manufacture. That taste, it's got a really, really fantastic sort of exotic taste, so we had some good fun with coconuts.
Yes, so nuts are actually really good for you. My problem with nuts is that I like them to be buried in copious amounts of chocolate - that's how I like my nuts; whole nuts, milk chocolate, that's my weakness in life. And as with so many things, you've really got to look at what's happened to them before you get them, before you start eating them, really haven't you?
David Shuker: Yes.
Paul Merrett: I'm thinking about dry roasted peanuts and salted nuts and things like that.
David Shuker: That's right, I mean, because this is one of the things about food that - if we think that something is good for you, there's two problems that you can get with things being good for you: one is that if something's good for you, a lot more of it would be even better for you, and that's not necessarily the case; the other thing is that, if you take a good ingredient, like nuts, and then you do something quite bad to them - like for example cover them with salt - then the net effect is probably that you almost undo the essential goodness.
So I think that's the sort of thing you just need to watch out for is that. I think, in general, nuts are a great source of food. They're high in protein, they mostly haven't got a lot of fat in them, naturally they don't have a lot of salt in them. But of course if you cover them in salt, then you undo that. So it's a question of just taking an ingredient or a food like nuts and treating them with a certain amount of respect, I guess, so you get the best out of them.
Paul Merrett: Yes, respect for your food, that's not a bad message. To find out more about the science of food, and to get any of the recipes that we've cooked on the series, and possibly a little bit more of me and David chewing the fat, visit our website at open2.net. I'm Paul Merrett, and I've been talking to David Shuker of the Open University. The producer was Michael Brodbin; this is a BBC Worldwide Production for the Open University.