Paul Merrett: Hello, I'm Paul Merrett, chef and presenter of the BBC Open University TV series Ever Wondered about Food? - and I am wondering about food. And quite luckily I'm wondering about it with David Shuker, who is the professor who's supported us with all the scientific facts right the way through the making of this series. Hello, David.
David Shuker: Hello, Paul.
Paul Merrett: And we've just finished making the Sausage programme, and - meat for me - is there's a whole range of scientific titbits to enjoy with meat, not least of all why it goes brown and at what temperature this happens and that happens and all sorts of things. But, just to talk about sausages for a moment, are you a sausage man?
David Shuker: I am, yes, I spent a few years living in France and so I broadened my sausage horizons as it were by eating some of the saucisson sec and all of the rest of it but, yes, I love sausages.
Paul Merrett: They know their sausages over there. Well, I think the Brits do as well. I think we've got a good tradition of sausage making, and they're no longer stuffed into intestines, are they, as some people think?
David Shuker: That's right. Interestingly that's right. I mean it was originally when, of course, people were using every bit of the animal. Of course, when one says the intestine, it turns out to be really the covering of the intestine which makes this sort of thin membrane, which turned out to be quite a useful tube to stuff things into, and so that's where it came from originally. But of course, although you can still buy sausages that are made in the traditional way, many of the sausages that we buy have a sort of synthetic covering. But, of course, it's entirely edible and is made from essentially the same material but made in a sort of more manufactured way.
Paul Merrett: Yes, in my professional capacity I buy natural casings from the butcher, and they come in salt. They're a very kind of dry bundle of casings, and they're quite grey, and you have to soak them really well to rid them of impurities - and the salt, I guess, as well before you make your sausages. But making sausages, actually, although we think that bangers are easy to cook and really nice to eat, they're actually quite difficult to make because you need to balance that protein and fat that you've got inside in order for the thing to have the sort of really rich taste that you want from a sausage.
David Shuker: Well, exactly. I mean, in a sense what you're doing is that when you're making a sausage, I guess, you're sort of preparing all the ingredients in one fell swoop, but in such a way that when you actually cook it in a pan or grill it or whatever, that it would actually cook properly and give you the desired flavour.
Paul Merrett: Yes.
David Shuker: It's interesting, actually, when you think about it, if you put a sausage into a pan, of course only a very small bit of this cylindrical tube is actually in contact, so it turns out that the fat in there, one of the jobs of the fat is to actually help to transmit the heat from the pan into the sausage, so it cooks.
Paul Merrett: So one of the things we discuss in the programme, more than once, is something called the Maillard Reaction, which is the name of the chemist who first understood the reaction that was taking place when heat was applied to a process.
David Shuker: That's right, the Maillard Reaction is interesting. It's been known for almost a hundred years, and you're absolutely right, Maillard was a French chemist who became interested in what was going on with this reaction, because he realised that when you cook meat particularly - but it happens to almost any protein - when you cook it of course you get this browning reaction. And he realised this wasn't sort of burning; it was actually a chemical reaction that was going on.
And it turns out that the amino acids that are the building blocks of proteins undergo a reaction with some of the sugars. Almost every food, even meat, contains some sugars - and it turns out these things combine to give you these products - what are called the Maillard products which actually contribute to the browning.
Now, interestingly, we don't still completely understand how that reaction works; it's actually an active area of research.
Paul Merrett: So it's not the sugars in the proteins caramelising?
David Shuker: No.
Paul Merrett: It's more than that?
David Shuker: It's actually a combination; it's actually a chemical reaction between sugar molecules and amino acid molecules, and they combine, and when the products that are formed actually have this characteristic colour. Interestingly, they also contribute to the flavour as well because they have characteristic flavours. So the Maillard Reaction is something absolutely crucial to a lot of what contributes to cooking and good taste, and also what food looks like.
And of course I'm sure many people are aware that you can cook many foods in a microwave, but the way that microwave cooking occurs means that you often don't get browning. And so you end up with food which is cooked but doesn't taste quite the same, it certainly doesn't look the same.
Paul Merrett: Does there have to be a direct heat applied?
David Shuker: It's actually the local heating that occurs when the meat is in contact. Many people, I'm sure, have noticed when you put a piece of meat into a pan you get very irregular browning, and of course it's why you have to keep sausages and you have to keep steaks turning over. The interesting thing about this, of course, is you can overdo it, and that's the thing that you have to watch out for; and that is that you can actually overcook the meat and this reaction goes on, and you actually end up producing products which are not good for you.
And some of these have been linked to cancer. It's often not very pleasant to talk about these kind of things in connection with food but the problem is that there's a fine balance between cooking food so that it's very appetising and healthy for us and overdoing it, and in this particular case, and certainly when you're barbequing, it's very easy to overcook because it's less easy to control.
Paul Merrett: So charring on the outside is not particularly good news?
David Shuker: Effectively what you're doing is you're overheating, you're pushing that reaction too far, and it ends up producing products which are actually deleterious; they're actually quite toxic.
Paul Merrett: Yes, I see. One of the big changes in professional cookery over the last few years, I think, has been our approach to cooking proteins. When I was a young chef I was taught to cook a sirloin of beef, for instance; seal it off fiercely in a pan to seal in the juices - which we now know isn't happening - and then throw it into a very hot oven, and then turn down the heat, cook it for a short time, take it out and rest it.
What we now do is, we don't seal the meat at all, we rub it with a tiny bit of oil, we season the meat and then we put it into a very cold oven. I cook a sirloin of beef at seventy-five degrees, and we cook it for maybe five hours, probing it all the time, until the core temperature reaches fifty-six degrees, which I've been led to believe is the magic temperature (that's when proteins de-nature), so if you're going to overcook the meat, that's the point that it's going to start happening -when the core is fifty-six degrees.
It seems to me that cooking now, certainly professionally, has become as much governed by the probe and thermometer as it has by the chef's eye. And the chef just knowing isn't good enough anymore - it's a far more scientific approach - but I do think it's led to much more consistent results. I don't know whether you feel some of the joy is taken out of cooking by doing it like that, or whether you enjoy applying a really scientific view to cooking?
David Shuker: Well, I mean, I think it's interesting hearing you talk in this way, actually, because I'm quite interested to hear you're almost talking like a professor of chemistry actually because you started off talking about proteins, the chef's approach to proteins. I would have thought you'd talk about the chef's approach to meat.
Paul Merrett: Well there you are, yes.
David Shuker: No, but that's right, but I think you're right, and it is interesting to wonder why that is. I mean, certainly I'm sure in a restaurant kitchen you want consistency - you don't want the sort of haphazard approach ("Well last night it worked but tonight it doesn't") and I think there's nothing wrong with that and, interestingly, I wonder whether the whole sort of food industry is probably what's driven a lot of this: the idea that you use things like temperature probes to check that any food is being properly cooked through, because there's problems if you don't properly cook meat or other dishes; you can get problems of bacteria and all the rest of it.
So maybe that's where some of that's come from, but I think certainly it's more fun in the kitchen if your cooking becomes more dependable and reliable, and if you can use some sort of scientific aids to do this, I don't think there's anything wrong with that. I mean, I still think much of what goes on in cooking is enough of a mystery that there's still that sort of pleasure of slightly, "Why did this dish taste particularly good today but…?" and certainly the traditional thing about why some dishes taste much better the next day, well of course a whole lot of chemistry has been going on and things. So it is a fascinating area, I think. Well, it seems to me that the more you understand about it, it actually doesn't detract from the fun of cooking, so I guess that's what it's all about.
Paul Merrett: Do you know something I don't understand - or something that I don't spend enough time trying to understand - what's all this mono- poly- hydrogenated - what's all the science about the fats that we find in meat? What do we need to know about before we eat a piece of meat in order to make the right decision about how often to eat it, or what type of meat to eat?
David Shuker: Well, of course, I mean the thing as well - okay, the monounsaturated, the polyunsaturated, the partially hydrogenated fats - basically a lot of the fats in meat are the saturated fats. Saturated fats we know from a lot of studies now are probably not particularly beneficial for us. I mean all fats give us energy, so they've all got a nutritional role. But all foods probably have more than just a single role, and it turns out that, if you're going to eat fat in your diet, it's probably better to try and get a balance of polyunsaturated fats, which appear to be the kind of fat which the body can use in a creative and positive way in a sort of metabolic sense, and there's been a lot of evidence and research which backs that up, which suggests that the polyunsaturated fats are better for us than the saturated fats.
Paul Merrett: I think one of the secrets to cooking meat successfully is knowing and understanding what cuts of meat are cooked in a certain way, so why would a neck of lamb take to stewing so much better than a fillet of lamb? And why would a fillet of lamb be far better roasted rare than a neck of lamb? And it's understanding the sort of - as a general rule of thumb, I think I'd be right in saying that the areas of the animal that do the most work generally need an extended cooking time because they are more fibrous; they have more connected tissue and that needs breaking down.
But I think people need to understand that theory. Is there any a more scientific way of looking at pieces of meat, and understanding, just from appearance, when you look at the piece of meat, being able to judge what sort of cooking that piece of meat needs?
David Shuker: Well I think you've hinted at or alluded to the key point, and that is that tissues, meat which contains a lot of connected tissue - that is the part of tissue which gives more mechanical strength - those parts…. For example, you mentioned the neck. I mean that's got to do a lot of work in supporting the head of both us and animals and so there's a lot of connected tissue. That requires much more breaking down to become digestible. And of course the whole point about cooking is… (why do we cook things?) …is because we want to make them taste nicer, of course, but also to improve their digestibility so that we can process them. And so, knowing which part of which cuts of meat need to be cooked in a particular way of course is probably vital. And just assuming that a piece of beef is a piece of beef is clearly not the case. That's the reason why, for example, not only is it the cut but the way that meat has been left to age.
I can remember, for example, going to buy a couple of steaks in a French butcher in the Dordogne years ago, and the butcher cut these off a piece of meat, and I thought, "It's a bit dark that, how long has that been around?" When we took them back to the campsite and barbequed them, well it was the most succulent cut of beef, and they just needed to be cooked very quickly on the barbeque - because that meat had been aged and the proteins in there were more digestible basically, and anyway it was probably a good cut of meat that didn't contain a lot of connected tissue and therefore it only required a very delicate cooking.
Paul Merrett: I thought you were going to tell us he'd sold you a bit of horse for a moment, and I'm glad to hear he didn't. Well, David, thank you very much. If you want to find out more about the science of food, or get any of the recipes from the series, or hear a bit more of me and David chewing the fat - literally in this instance - visit our website at open2.net. I'm Paul Merrett, and I've been talking to David Shuker of the Open University. Our producer is Michael Brodbin, and it's been a BBC Worldwide Production for the Open University.