Instant Genius - The science of cooking, with Dr Stuart Farrimond

Episode Date: June 14, 2021

Food scientist, doctor and TV presenter Stuart Farrimond tells us about how you can use science to upgrade your cooking. Once you’ve mastered the basics with Instant Genius, dive deeper with Instant Genius Extra, where you’ll find longer, richer discussions about the most exciting ideas in the world of science and technology. Only available on Apple Podcasts. Produced by the team behind BBC Science Focus Magazine. Visit our website: https://www.sciencefocus.com/ Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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ideas in science and technology today. I'm Sarah Rigby, online assistant at BBC Science Focus magazine. In this episode, I talk to food scientist, doctor, and TV presenter, Stuart Faramond to find out how I can use science to upgrade my cooking. So first of all, to be a really good cook, what equipment do I really need? Hey Sarah. Yeah, great question. So the right equipment, and this is really hard. And I'd tell you what, probably the most important thing is your knife. And you know, you will ask a chef, a chef will carry out his knives because the knives are really important because obviously need to chop things. But a knife is more than that. You know, I would say the most important thing is a chef's knife, which is one of those ones that's a sort of a V-shaped thing, a V-shaped knife. And the good thing about that is that it's got a very large edge. And so you can actually use it for lots of things. You can crush garlic with the side of it. And because if it's got a curved edge, then you can do it, you can do like a rocking movement,

which is great for, great for chopping herbs, doing things very quickly. So a knife is really important. And what you'll find is that if you say to somebody, I really like some good knives, like save my birthday or something, then you'll often end up with a block of knives. I mean, you're nodding. You've probably got a block of knives in the kitchen. Now, have you used, use all those knives? Yeah, I think I have used all of them, actually. But are there some that you just rarely ever use? They're just sort of an odd size.

Yeah, absolutely. And what you find is that there's normally two knives in a block that are used for. Your big chef's knife and maybe a small one, or a medium size, which you call a pairing knife. And you've used a serrated one. That's quite useful. And you might have a sort of a longest, sharp one, sort of a carving knife. So basically only to buy the knives that you use, you don't need.

like a fish knife and all these different things. So pick the knives, so keep it simple. Get yourself a good chef's knife. A serrated knife is really useful, and you can actually get away with serrated knives without actually not getting such an expensive a serrated knife. And that is because when you zoom right in to a serrated knife,

it cuts because all the little sort of the downward sort of scolloped, shaped parts of the blade, as you cut, you cut by pulling, and as you pull, each of those tiny little points gets a little nick into the food and it tears it. And then once the nick is in there, and because you've got all these large points, you can very easily cut into things. So you know, if you've got a blunt knife and you're trying to cut into a smooth tomato, it's very difficult because it just slides off because the blunt edge can't cut into,

can't find a nick to get into in that very smooth surface. But with a serrated knife, you've got all these points that's very easy to cut in. So serrated knives are really good for cutting. bread for cutting, you know, things that are very waxy that you find difficult otherwise. So there are things to bear in mind. And what about pots and pans? When should I use stainless steel? When should I use cast iron? Yeah, cast iron is quite trendy, as is copper. Cast iron is very good because it retains heat. It's very heavy. So the benefit of cast iron is that once you've got it up to temperature. You can cook your steak in it. Either can then take the pan off the stove and it will keep things hot for a long time. The problem with cast iron is that you need to look

after it because basically got to be very careful with scouring devices. With cast iron, it takes a long time to heat up. So you need a variety of pans, should we say? So yes, it's worthwhile having a cast iron skillet. If you're going to be doing things like like steaks or something that you're going to be griddling like that, if griddling is the right word. So yes, so cast iron is good. Copper is similarly very heavy, and because it's heavy, it takes a while to warm up, but it's very good at distributing heat. And by that I mean is that you don't get hot spots so much. So if you get a cheap, thin aluminium frying pan and you put it on your flame, you'll find that the heat doesn't spread out very much. So you end with a hot spot in the middle where over the flame,

or the electric element is. So it becomes very difficult to heat things evenly. So if you're trying to, say, make an omelette, you'll find that the middle of the omelette gets cooked before the outside, because the heat isn't being distributed across the pan. And there's lots of arguments about the different metals, but essentially it's the thickness of the pan that is most important. When they've looked at it scientifically,

and they've said, you know, what's better copper, iron, stainless steel, aluminium, or there's some way you can get them, they're sort of, their sort of sandwich, so you can have like the three plies. So you'd have stainless steel on the top, the stainless steel on the bottom, so it's really easy to clean and it won't rust or corrode. And in the middle, you have something like copper, so that helps distribute the heat. And they perform very well in scientific tests. The only problem is they're very expensive because I'm sure you can imagine getting three layers of metal together in that way and shaping into a pan is pretty hard work. So, but essentially

the thicker, the base of the pan, the best it's going to do. distribute heat. People say a lot of things about non-stick that you should avoid non-stick because at very high temperatures. The non-stick covering coating is said to flake off and it's apparently toxic and it's not good for you. I would say you probably don't want a non-stick for doing super high temperature cooking, like really hot stir-frying. But apart from that, they're really useful for sort of frying an egg, you know, because, you know, it's very difficult to get an egg to stick to you stick to the surface of the pan if it's non-stick. And the reason why when you cook with something and it sticks to the pan,

essentially what's happening is proteins react with the metal atoms on the surface of the pan. And there's a chemical reaction that goes where the protein fuses at high temperatures to that metal. So actually when it's sticking, there are actually bombs that are forming between the pan and the pan metal and the food itself, which obviously you get that if you try to get the skin of your fish, really crispy and you don't get it hot enough, then what happens when you don't have enough oil in there, then the fish or the food, whatever it is, is allowed to come in direct contact with the metal, and so it then sticks. So the solution to that is non-stick, plenty of oil and keep it moving. But essentially what I'm saying is that non-stick isn't actually as evil

as many people say it is, and lots of top chefs will have a non-stick frying pan in their kitchen because it's just useful. Okay. So that's, Let's talk about cooking meat. So often when you cook meat, you want a nice brown layer on it. It looks really nice, but does it do anything more than just looking nice? Yeah, one of the things, my mum has never been a very good cook. And her idea of, say, like a stew or something would be to get a big broth of something very simple, not very well-flavored.

And then she'd throw in some various vegetables. She'd throw in some meat maybe. And at the end you end up with this bowl. of something and the meat is pretty bland and tasteless. And what the problem is, is that for meat, most of its flavour comes from the outer surface, that brown, lovely, meaty, sort of, that, that thing that we all love, the smells of the barbecue, that, that meaty outer coating. And what's going on there, what gives that the meat its flavour is a reaction called the meyard reaction. It's spelled mallard reaction, but you pronounce it, Mayard reaction. And essentially,

what's happening is that when the surface of food gets above about 130 degrees C, then the bits of the protein, proteins are made up of substances called amino acids, and when those amino acids react together with the traces of sugar that are in all foods, basically all foods have little traces of sugar in, and they react with the amino acids. And these bizarre things happen. There's a sort of this this kind of clashing together of these two things. And there's a, there's sort of this cacophony of different reactions that take place. And it's sort of these, these almost infinite sort of different combinations of one molecule clash with another molecule that gets bigger and then that clashes with another one. It's all happening on the surface of the food as it's cooking at this temperature.

This is called the mailed reaction. It's also called the browning reaction because many of these substances that are formed are brown. But these substances that are formed, they're very aromatic. They have a smell to them and that's what gives it their flavor. They're called flavor compounds and the vastness of all the different reactions and the possibilities that can take place are what gives individual foods their unique flavor based on the types of proteins on the surface of that food and the types of sugars and the amounts of sugars that are there, those trace amounts of sugars that are there. And that's what makes meat taste like meat, steak tastes like steak is the same reaction fundamentally the same reaction that happens on bread

when you put it in a toaster and it comes out and you transform bread into toast. You know, like as a kid, you go, well, the bread goes in, but where does the toast come from? Because it's so different. And that's because this wonderful reaction. So if you don't brown your meat, so my mum, for example, she wouldn't brown the meat, she'd just chop it up and throw it in. The meat is never going to go above 100 degree C, the boiling point of water. So it's never going to brown. The only way to get that meaty flavour on any kind of meat or fish-based food is to cook it at that high temperature. So you've got to, say, fry it off beforehand. And you'll see, if you get a thermometer and you put it on the pan, you'll see that as it goes above 100 degrees C, which you can only do if you've got oil

rather than water in the pan because oils go to extremely high temperatures before they break down and they catch a light. So you need oil in the pan. As it goes above 130, 140 degrees, see all of a sudden this magic, you get smells, these kind of roasted, nutty kind of smells that fill the kitchen. Same thing happens with baked bread. It's that same reaction going on that gives food its wonderful cooking flavors and smells. Browning is essential for all. or meat cooking. So let's talk about eggs for a minute. I like poached eggs, but I'm rubbish at making them. So scientifically, what's the best way to poach an egg? That's a great question. I actually went on to this morning, the ITV program once, when there was a couple of years ago, around

that time this book was originally brought out two, three years ago. There was a big hoo-ha, should we say. It was a slow newsday on how to cook the perfect poached egg. I think it was Nigella Lawson or Delia Smith had decided that they had the best way to poach an egg. So they wheeled me out to say, scientifically, what's the best way to poach an egg? So essentially, the first thing you've got to bear in mind when you're poaching an egg is that there's a yoke

and there's a white. Whichever goes, yeah, there's a yoke and a white, but actually there's two whites. There's a thick white and a thin white. When you crack open your egg, put it in a bowl, you'll see you've got the yoke, then you've got this thick sort of very gloopy egg whites around it, then there's a thin sort of watery egg white around it. And so the mistake that people make is that when you dunk it all in is that that thin white around the outside cooks very quickly and it ends up

as this very stringy kind of mess. And so you're trying to keep it together and your pan's just filling up with this thin white that's getting cooked and just making it look horrible. So one way to get around that is to get a sieve or a tea strainer and you can, when you crack the egg, crack it into that and then a little bit liquid will come off. That will be the thin egg whites. If you really want to, you can keep it to one side and use as part of making meringue, for example, but essentially that's not going to make a good poached egg. You then want the pot on a, on a light simmer. You don't want it on a high rolling boil, on a light simmer. You want to put in a little bit of salt, a little bit teaspoon of salt and a glug of vinegar. And what you will find

is that when you put it in there, a reaction goes on with the albumin, the egg white, and the acetic acid, and it produces carbon dioxide. And with the salt added into the water as well, those little bubbles of carbon dioxide change the buoyancy of the egg. And these little bubbles of gas will cause the post egg to rise to rise to the surface as it cooks. And so what you're fine is that you can put the egg in there. And as it rises to the surface, that'll tell you pretty much that it's done. So that's a nice, neat little way of, and trying to get it about the timing about right. So you don't need to swirl it, as some people say, it doesn't really make much different. You use a slotted spoon as well. So that helps you sort of get it out.

I mean, the worst thing is when you're trying to fish it out with a regular spoon, you're trying to squash it up against the side and it's all going horribly wrong. So yeah, there's just some tips. You know, everybody's got their own personal idea about it. But, yeah, a bit of salt, bit of vinegar, adds through a bit of the flavour, put it in there, wait for it to rice, the surface, don't put it on too much a rolling ball, and get rid of the thin white at the beginning. Wow, okay, I didn't know that about rising when it was done. That's really interesting. So it's become a bit of a cliche with eggs that we keep changing our mind about whether they're good for us or bad for us. So what's the consensus?

To be honest, I think at the moment the consensus says that eggs are generally good for you. eggs have relatively high amounts of cholesterol, which is the thing that everybody gets worried about with their heart. And that was initially the reason why eggs were said you don't want to eat eggs because it's bad for your heart. The thing is that that cholesterol doesn't actually, unless you have lots and lots of eggs, doesn't actually translate to high levels of harmful cholesterol in the blood.

So essentially, so eggs have huge amounts of nutrients in there. They've got a great amounts of protein. There's a good ratio of proteins to the fats. So yeah, they're little nuggets of excellent nutrition. So on balance, I would say eggs are actually really good for you. They recommend, I think, no more than about check the numbers. But you don't want to be having more than one or two a day.

That's probably more than enough. So, yeah, so eggs generally, I'd say they're on the favoured size of things at the moment. Right. Well, that's good to know. So I've got my meat and I've got my eggs. So let's talk about vegetables. One vegetable I particularly like cooking with as onions. I love onions in basically every dish, but they always make me cry when I chop them. So how can I avoid that? Yeah. Essentially, there's a protective reaction going on inside the onion. Onions, like many plants, don't like to be damaged. And their protective mechanism is for a series of

reactions to take place inside them. They've got they've got little, they've got bits of sulphur that are locked away, ready to be turned into this potent, nasty, sulphur-containing vapour is the thing that makes your eyes water. And it only comes out when the onion cell has been damaged. So as soon as you start to cut it, you're chopping through these cells, this reaction goes on of these sulphur-containing substances. They react together. They turn into a vapour that they they come up and they reach your eyes and it turns essentially into a sulfur-containing acid on the surface of your eyes and that's painful and it makes your eyes run. So as soon as you start to cut that onion and there's air between you and the onion, your eyes are going to feel it.

So what you can do to get around that is you can put tight fitting goggles on. You can cut, you can cut beneath water if you want to. Some people do that is quite tricky to do. you can get a very sharp knife because that means that when you cut through it, you're causing the minimum amount of damage, you're crushing the least number of onion cells possible. If you cool it, so you put it in the freezer before you chop it, that slows down all enzyme reactions. That slows down all the reactions so that when you cut it, that reaction that makes this nasty, sulfur-containing vapor won't take place as quickly. So there's some, there's some nice, it gets good ventilation, open the window,

get a fan blowing across, and then you can, they'll blow it away, blow away those nasty vapours. Great, thank you. Spoon in the mouth and all those things, a load of rubbish. And now the last most difficult thing probably that I want to ask you about in cooking terms is chocolate. I've had a lot of trouble with tempering chocolate. So could you just give us a brief outline of what tempering chocolate is and why you need to do it. Yes, it's a tricky one. And I was mentioning to this before we started recording was that chocolate doesn't like to mix with water.

So this, I guess as a separate aside, is that chocolate doesn't have moisture in it. It's essentially moisture less. You can kind of think of chocolates being made up of lots of particles that hate water. They like to stick together. They're oil-loving water. are hating. And so what happens is that when you add some water to it, you end up with these

fat-loving globules forming it on the outside of the little droplets of water. You end up with this big, claggy mess. And there's no way you're going to get it back to chocolate after that point. So if that happens, then you should keep adding water and essentially you end up diluting those claggy bits into essentially a hot chocolate. Or you can add cream instead and then you get a nice sort of lovely sort of ganache. So if you add water to chocolate, then that is a problem. You best just abandon it and turn it into a ganache. In terms of tempering chocolates, the thing that gives chocolate its lovely kind of texture, its lovely crunch, is the fat crystals in it that come from the cocoa butter. The thing that makes chocolate, the wonderful thing, the mouth-filling,

lovely sort of flavour that we get from chocolate, is that it melts at just below body temperature. So when you get chocolate and you put it in your mouth and you leave it in there, it melts. And so all those flavor compounds are released, all the vapors are released into your nose, go up the back of your mouth, into your nose, and you get all those flavors. All the lovely sweetness comes out. So that's what makes chocolate because it's lovely texture. And the straight thing is about cocoa butter. Cocoa butter is essentially just the word for cocoa fat. It's the fat that you get from the cocoa bean, if you like. When it's been fermented, it's been processed, it's been, it's been separated into its cocoa solids and its fats. So the fat has been taken out. The fat is the very expensive

thing. You don't get a lot of fat, what we're called cocoa butter from your cocoa bean. But that is the thing that gives these chocolate its unique texture and mouth melting properties. But to temper chocolate, so you get that lovely crunch, that lovely mouth melting sensation, is you need to get cocoa butter into the right solid form. And when you solidify cocoa butter, it's made up of lots of different crystals, which are sort of graded from 1, 2, 3, 4, 5 in Roman numerals. And each of these crystals has different melting and solidifying properties.

And what happens is that if you melt your chocolate, which has got its cocoa butter in, and you allow it to cool to room temperature, you end up with lots of jumbles of all the different crystal, crystal shapes and forms as it all sort of comes together. But if you call it slowly and you cool it carefully to a temperature of about 28 degrees C and then stop, and then warm it again a little bit,

just about 31 degrees C, then you end up with a wonderful lattice of the number 5 crystal, which is the one that has the best texture and the best mouthfield to it. So you need to look at the temperatures. Check out a book so that you've got the temperatures right. Cool it. You need a thermometer, then warm it up again, and then allow it to cool down to room temperature, and you will end up, it's a real fiddly job, to be honest.

And if you fail, that I wouldn't worry too much about. There's all sort of different techniques, and you can use a blade on a marble surface to sort of control the temperature better as you're doing this cooling and heating process. So that's the essence of. it, but it's not something that I've had much success with. I'll be honest with you. Okay, great. Thank you. So of everything we've talked about today, what would you say are the three things I really need to know about food science to become an instant genius?

The Mayard reaction. Everything that tastes good pretty much has had the Mayard reaction happen to it. So make sure that you cook things using the mayo reaction. So even if it's nuts or seeds, put them in a pan, a dry pan, give it a shake, a keyed up to about 130 degrees seat, get it roasted, get those flavours, meat, always brown it beforehand, fish, always brand it beforehand, vegetables, still have protein and those traces of sugar when you get, that's what makes roast potatoes,

roast vegetables taste wonderful, use the browner reaction in as many things as possible. I'd say that's really important. Don't underestimate flavour and salt is the most common, most popular flavor enhancer because it is so good. It's something that our body craves in nature. Salt is very difficult to come by. And unless you happen to live by the sea or by a salt mine, you wouldn't come across salt very much. And it's essential for life. So we're driven to salt. So little bits of salt in food just make it taste so much better. We evolved to enjoy it.

And it actually makes sweet things taste a little bit sweeter. So yeah, don't be afraid of using salt. obviously don't use it too liberally for health reasons. But I'd say there two things. You want a third one. Oh gosh. Third one. So we've got browning, we've got salts. Out of all cooking, you want a third one.

Sorry. I guess cook things that you like. Because food is to be enjoyed. And there's few things in this world that forces to sit down and be with other people and commune, if you like. So I think make it. part of the ritual of eating, of enjoying, of enjoying the cooking together and do it, do it because you love it. I use it as a way to understand science a bit more to go,

oh, you know, that's really interesting about that May-Reyreaction thing. And actually that means I can cook a bit better and I can understand a little bit of what's going on in my food. So yeah, have fun. Thank you for listening to this episode of Instant Genius. That was Dr. Stuart Faramon. If you want to know more about food science, check out his book, The Science of Cooking, to hear him tell me how to upgrade my whole life using science, head over to the Instant Genius Extra podcast. The June issue of BBC Science Focus magazine is out now. Pick up a copy in store or visit

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