The Science of Cooking: What's Really Happening to Your Food | with Ben Ebbrell & David Weitz

追加: 2026-05-19

[00:00:05]Bread is an amazing thing. Quite literally, companionship. Companionship is breaking bread together. Compan the literally the ethmology of the word.

[00:00:15]Everywhere in the world has their own bread. And you're turning the most simple, humble of things through fermentation and yeast into bread. And you get this wonderful structure that is bouncy. And I chose ficatcha because it's the bounciest of bread. lots of air and elasticity. So much so that David said, "Do you reckon we could do something with that?"

[00:00:34]>> Could we measure the elasticity? How elastic is it? Well, let's understand what elasticity really means. So, what's elasticity? Elasticity is a spring. So, if I have a spring, what happens? If I hang a weight from a spring, imagine I have a spring and I hang a weight at the bottom of the spring. What happens?

[00:00:53]It goes down, right?

[00:00:56]And how much it goes down depends on the spring constant depends on the elasticity of the spring by Hook's law.

[00:01:07]So the elastic constant of the spring depends on the force and how much it uh it it it extends. But if I want to describe something like this bread, I don't want to think of it as a spring. I want something that's independent of just the size, the shape. So what we do is we uh discuss an elastic constant and sorry and the elastic constant is given by this.

[00:01:39]We take the force and we normalize by some area and we make take the displacement and we normalize by the size of that that it was. So this I can calculate an elastic constant and I've done this enough that I can tell you what elastic constants of different foods are. I can tell you what elastic constant. I know what things feel like just by measuring it. And this is called realology. And I always say I do digital realology because I can do I can feel with my digits what it's like. But we can do this here. We can measure the elastic concept because it tells us what to do. We need to apply a force. We need to know an area. And we need to know a displacement. Well, here we have a piece of fkaca that we cut the I measured the size of it. Actually, it's gotten a little stiffer now because it's been out. It hasn't held the moisture because but it's okay. I made the measurement before. We'll do it again. And so, what we have to do is we have to apply a force and measure displacement. So, can somebody come and help me with the camera? I think we need somebody who knows how all the to operate the camera.

[00:02:51]This won't give me the same result as it was before, but Oops.

[00:02:58]Oh, the camera went off. Sorry.

[00:03:06]>> Oh, sorry. Don't get sick, everybody.

[00:03:10]>> Okay. So, now you can see what I'm going to do. I've measured I have a I have a ruler here and this is about 3 and a half cm. I did the calculation. I did the measurement a little earlier and I can just feel with my hand that it's much stiffer now because it's dried out.

[00:03:26]>> Maybe we should cut a new piece for ketchup.

[00:03:31]>> I need it 3 and 1/2 cm by 3 and 12 cm by three.

[00:03:40]It's okay.

[00:03:44]This is doing real real time experiments.

[00:03:48]>> Do you know what? That's so airy that's not even got the right.

[00:03:54]>> Okay. No, no, let's do both. Let's do both. Okay. So, now this is 300 g. Do we have the extra weight somewhere? Let's see. So, let's see what happens when I put the It doesn't deform it at all. Okay. Well, this got a lot stiffer, you know.

[00:04:16]This is 300 g, 400, 500, 600.

[00:04:25]I think it may work. Let's try.

[00:04:31]I think that bread's just about fit for a duck.

[00:04:35]It's deformed a bit. So, let's do it.

[00:04:37]Now, I'll I can do the calculation. I can tell you how to do the calculation, but let's do it with a fresh piece.

[00:04:45]And here, I'm going to take off three of them because I know from before that it's what it's going to be like.

[00:04:56]So, what's that? It's about uh this is about four and a half 300 300 g.

[00:05:09]It goes down to about three and a half, right?

[00:05:14]No, it went from 0 1 2 3 and a half. It's about four and a half. So, it went down about about a quarter.

[00:05:24]Okay, I did the calculation. I did it with a slightly different size. I'm going to just show you. This is what I did.

[00:05:34]I did this. And so I'm going to calculate it. I need the I I need the force. I need the area. I need the deformation.

[00:05:44]This is the equation.

[00:05:48]And these are the the numbers I did before, but it's more or less the same.

[00:05:52]The size is about 3.5 cm squared. This the other piece was 3 centimeters. This is four and a half. It doesn't matter.

[00:05:59]The deformation was about 1/3 before with 300 g with uh uh.3 kilograms. And if you do the calculation, the the units are force over area, right? There's force over area divided by length over length. Length over length has no units. Force over area has units of a pressure. And that's the unit of elastic constants of pressure. And this is about eight seven or eight kilopascals. And I know from doing many many measurements that if you think of a rye bread or something like that, it's much stiffer. So there's much less deformation. If you think and this you can tell what it's like if you bite into it. If you have to bite really hard, the elastic constant's really large. So tough meat has something like 60 or 70 uh kilopascals. This is much softer.

[00:07:00]There's about a factor of 10 less soft than really tough meat. So this is really very weak bread and that's what uh Ben said. It's really springy. It's a very low elastic constant. And that's how we can parameterize it. That's how we can characterize it. So Ben, what else can we do?

[00:07:17]>> We do all sorts. You can see the oil and water separation. Did no such thing. And if we move on, I thought because I knew that there's a guaranteed way to get a round of applause is to make a dessert.

[00:07:32]So, that's what we're going to do. And we're going to start with an absolute classic, which is um meringue. Um and then we're going to turn the meringue into the hero of a classic dessert called Baked Alaska. a dish that we've made on the channel literally 15 years ago, again about 12 years ago, again about four years ago. We done so many versions of baked Alaska and I love it because of the wow factor. And the wow factor we're going to do again today, but hopefully we're going to get explained as well. So in here, egg whites and I'm going to whip those up.

[00:08:02]And in here, I've got sugar syrup. So that's just uh caster sugar dissolved in a little bit of water. And what I want to do is >> So Ben, excuse me. We're taking just a liquid, right? Egg whites. It's a liquid and all he's doing is he's mixing it.

[00:08:17]So, what are you putting into it?

[00:08:20]Air. Mixing air. Air goes everywhere.

[00:08:24]Right. Everywhere. Liquid goes all over the floor. Let's watch what happens.

[00:08:30]Now, there's a couple of different ways of making meringue. Uh, just whip up your egg whites, slowly dust in uh caster sugar bit by bit, and you have a French meringue. It's kind of not cooked out, but it's great if you're going to put it through the oven, low temperature, crisp it up for something like a pavlova. Alternatively, the Swiss mering where you do this process pretty much over a bayarie and you're kind of warming up to a consistency that melts the sugar, stabilizes it a bit. Or the Italians, they know what they're doing because with Italian meringue, you just streamline the whole thing super quick and easy. As soon as we've got a nice uh consistency on the egg whites, we take our sugar syrup, which we've heated up to 118° C. And then you can >> show us what the consistency is.

[00:09:11]>> Pour that in.

[00:09:13]>> You have a spoon or something.

[00:09:13]>> Have we got the camera? I don't know if I can do both.

[00:09:19]>> Dan, could you camera? Oh, here we go.

[00:09:21]>> It's worked. Oh, good. You see, it's almost solid like, right? The real test is whether you can hold it over your head.

[00:09:30]>> But you see the lumps. If it were liquid, it would flow. It would be even.

[00:09:36]>> What started as a liquid is now solid.

[00:09:42]>> So we have a solid through that emulsion of air and now we're going to add in all of our sugar syrup while it's whisking away. This kind of cooks the meringue in real time. So sugar syrup 118 and you dribble it in full speed.

[00:09:57]and you stabilize into this wonderful glossy meringue that holds a bit longer.

[00:10:04]Used in a lot of different desserts and pastry. Adds volume to this, but the heat is cooking the egg white beautifully glossy. Italian meringue.

[00:10:15]Can we talk about the solid like nature while you're doing that, >> please?

[00:10:20]So, why is a foam it's liquid and gas becoming a solid?

[00:10:26]It's the same physics. Now it's air drops. It's not liquid drops. And when they pack, they become solid. They behaves exactly the same way. So guess what? The equation is the same.

[00:10:49]Other component for baked Alaska, you got the meringue. Uh, you got a little bit of sponge on the base. Here's one I prepared earlier, proper Blue Peter style.

[00:10:58]But there's also this bowl of ice cream in the middle and then you torch the meringue. But the miracle is this ice cream in the middle remains frozen. So, we need to make ice cream. And Dan has a great way of making ice cream using not my muscles, but all of yours.

[00:11:16]>> Okay. So, we've got some sort of ice cream mix in here. What would be in there, Ben?

[00:11:21]>> A custard. a custard base. So, uh, cream sweetened with sugar but thickened with egg yolk and you end up with a nice custard base.

[00:11:29]>> Okay. So, in goes our custard ice cream mix into the bag. Um, we want to make it cold. Some ice. We got some ice, Ben, for me to put in another bag.

[00:11:37]>> Absolutely.

[00:11:40]Get the air out of there.

[00:11:46]So, would you mind filling the bag with ice there? Now, is this ice going to be cold enough on its own to make our ice cream?

[00:11:52]>> I don't know. It came from the freezer.

[00:11:53]And ice cream lives in the freezer.

[00:11:54]>> Pretty cold. But we want it to happen quite quickly. So, we can lower the temperature in here by adding some salt.

[00:12:00]And that lowers the freezing point of water. So, this ice will start to melt, but it will go below 0° Celsius.

[00:12:09]Put loads in there.

[00:12:11]There we go. That's not the bit we're going to eat, so don't worry about that.

[00:12:14]Um, I'm going to put our ice cream mix into the middle of there. I'm going to seal that up.

[00:12:22]And just in case, I'm going to put this bag in another bag. Oh, if I can get that.

[00:12:27]>> Safety first.

[00:12:28]>> Get the air out of there. Thank you very much, Ben.

[00:12:34]And then what we're going to need to do is mix this around. Now, it's going to get easier and easier as the ice starts to melt, but it's going to take quite a bit. And Ben's busy. I can't be bothered.

[00:12:46]So, I'm going to pass to you, sir. Um, now, because this will get below zero, it it will get cold and I don't want you to get absolutely exhausted. So, do this. Shuffle it around for a little bit and then pass it on. And we're going to try and get it sort of go up that way.

[00:12:59]Someone will have to pass it across the the steps. It go all the way across there. Someone will pass it across steps back down there. And if we can get it down to the gentleman in that corner there, we'll pick it up and we'll see if it's frozen by the time we get to it.

[00:13:08]I'm having trouble sealing this bag up.

[00:13:11]>> There we Now, traditionally, ice cream would churn long and slow. Going back to our love of Italy and things like gelato, an ice cream machine will churn, keep that moving as it cools down, but it might take a long period of time. Can we get this to work with the ice and the salt in about 15 minutes? That's the challenge.

[00:13:29]>> But if you're really lazy and you can't even wait 15 minutes, there is another option. And the other option is we call it a cheats uh ice cream. And in here I have clotted cream and uh creme fresh full fat, a little bit of icing sugar and frozen berries. Now the berries have to be frozen because what you're going to do is take fridge cold creme fresh and clotted cream and frozen berries and you blend them together. And as the blade does all the work, much easier than all of your work, what you end up with is it brings down the temperature of your dairy fat and your sugar. Uh, and you end up with an incredible really fruity and vibrant delicious instant ice cream. So, much like the pull through mayo, you might get a kind of vibe going on here is if I can find a hack and a shortcut, we will. And that's what the channel's been built on for years, teaching people to fall in love with food again and find all sorts of hacks and cheats. Question is, have I plugged it in? We'll see. Uh, blend it up.

[00:14:28]And it's churning, churning through.

[00:14:30]Now, you can do this at home. It's pretty instant, pretty quick. The temperature of the berries creates instant ice cream. Alternatively, when you're at the RARI, you can also get really geeky, can't you?

[00:14:48]I have always wanted to do this.

[00:14:51]Liquid nitrogen is going to take it right the way down. Even more so, there are ice cream parlors in uh London that serve and make ice cream to order using this method to take it right down as we pour a little bit in. It takes the temperature right down and we get this wonderful frozen ice cream but beautifully smooth cuz the blade is doing all of the work to get that creamy raspberry uh settlement down. And as simple as that. It takes seconds. No churning and churning and churning. No mixing and mixing around the bag. In no time at all, we have ourselves instant ice cream.

[00:15:32]>> Ben, can we can we ask what it is?

[00:15:38]So, what is ice cream? Ice cream is interesting. It's both a foam and an emulsion. It's got bubbles of air.

[00:15:47]That's what you mix it with. But it's also got uh drops of uh fat which are like the emulsion. So the emulsion covers the bubbles of air. Actually, it's even got solid pieces of the ice and that gives it its character. That's why you have to cool it. So it's an amazing material, but it's just really a combination of what we've talked about, both foams and emulsions. And here's a an image of it with taken with the microscope. And you can see that there's uh bubbles of air and drops of fat. And you can't see the solid particles, but they're here on the edge. So, uh an ice cream is really what we've been building with everything, but all combined into one material. That's a great dessert.

[00:16:37]Now, we have ourselves Italian meringue.

[00:16:39]In an ideal world when we're not doing this live, you know, when you can actually edit bits out on the internet, you'd probably leave that mixing a bit longer because this is still slightly, remember, we poured 118° syrup in there.

[00:16:49]You just keep mixing until it comes down to room temperature. But once you have it, you have this amazing stable, super super stable um meringue that is glossy and beautiful that you can put out and it holds. It holds so much easier if you're making dessert and leaving out on a buffet table or whatever. It's absolutely perfect for that. We don't have the time, so we're going to move ahead a little bit quicker because what I want to do is put this ice cream on top of our sponge.

[00:17:18]Sounds like we're getting good ice cream up there as well.

[00:17:22]We're going to seal it in with our meringue. Importantly, make sure there's no gaps and holes. And then you should be able to torch the meringue without melting the ice cream. Now I mentioned this to Dan and he was so confident of the physics. He had an idea.

[00:17:47]So this foam is going to be a super good insulator. You reckon it's good enough to to uh protect the ice cream? We've got a Harvard professor here saying it's good enough to protect the ice cream.

[00:17:55]And if it's good enough to protect the ice cream, I think that your meringue Ben is good enough to protect my hand from a blowtorrch.

[00:18:04]That's why you came this evening.

[00:18:08]I'm good to use all of that.

[00:18:10]>> Go for it.

[00:18:11]>> Okay.

[00:18:13]Now, I haven't worked in like a Michelin starred restaurant or anything.

[00:18:16]>> Nor have I, mate.

[00:18:17]>> Um, so excuse my technique.

[00:18:23]>> Oh, that it's warm. Yeah, it's still a little warm.

[00:18:27]>> Okay, I'm gonna make sure I'm all covered in steel.

[00:18:32]>> No gaps, Dan. No gaps.

[00:18:34]>> Um, I'm right. Am I right, David?

[00:18:35]Thinking when people see a good dessert, they're supposed to applaud. So, what's happening now? Yeah. Thank you. Thank you.

[00:18:42]Okay.

[00:18:44]Oh, little bit of exposed finger there.

[00:18:46]Okay. So, just to prove my fingers are still under there, right?

[00:18:54]That's a good make of a whisk, right?

[00:18:56]>> Yeah. Yeah. Yeah. That's good.

[00:18:58]>> Okay.

[00:19:00]Well, I'll start gently.

[00:19:03]Okay.

[00:19:07]>> Yeah. Oh, it's browning. There we go.

[00:19:09]>> And you're not yelping yet.

[00:19:11]>> No. In fact, I mean, I know I know we've probably gone a bit beyond what would look nice, but I want people to know that my hand is completely fine. I'm really going to torture. There we go.

[00:19:22]How about that?

[00:19:30]>> I think you might need to go and find yourself a tap >> and I got to clean up. Now there's a brave man which makes this all of a sudden look slightly underwhelming, doesn't it?

[00:19:43]But this is a fantastic simple torch dessert. You get that caramelization.

[00:19:48]Remember the sugar's already at syrup point. smooth all the way through, but you get those wonderful colors and lines inside our frozen ice cream. Lovely bit of sponge. Think of the flavors you can mix up throughout the year. Garnish it, of course. And that is a delicious dessert.

[00:20:10]Ben, are you are you going to cut it open to see if the ice cream's still frozen?

[00:20:14]>> We absolutely can. We probably should do that science.

[00:20:17]>> Got to do the science as well.

[00:20:20]We go right through the middle and we still have the >> Oh, look at that.

[00:20:24]>> Inside.

[00:20:31]>> Isn't that lovely?

[00:20:32]>> Beautiful.

[00:20:34]>> Ah, Ben, I think we're coming to the end.

[00:20:36]>> Yep. And I'm thirsty.

[00:20:38]>> Yeah. I think What do you do at the end of the a lecture?

[00:20:43]>> No. What else?

[00:20:45]>> A cocktail. A drink. Oh, let's have a drink. Should we try a drink?

[00:20:49]>> Let's have a drink.

[00:20:51]>> A couple of things to think about.

[00:20:55]>> Let's make a classic gin martini. And more importantly, let's ask ourselves why.

[00:21:03]So, what do we have here? Let's have a little think. Uh little jar. So, make enough for a couple. David, how about that? Uh some beautiful gin. This is a nice London uh craft facility based in Camden, so not far from here. Yum, yum, yum. What's the temperature of that?

[00:21:20]>> Well, it's been here all afternoon, so it's kind of room temperature, I would imagine. Do >> you have a thermometer?

[00:21:24]>> We can absolutely test it. Let's We should do really. That's science, isn't it?

[00:21:28]>> I do a lot of guesswork in what I do.

[00:21:30]And you keep insisting on testing things, David.

[00:21:33]>> We make measurements, right?

[00:21:35]>> Do you have a thermometer?

[00:21:37]>> Yep. Little bit of a mouth. I'm going to put the whole mix in here. So, we've got these two at room temperature.

[00:21:42]Beautiful.

[00:21:44]>> Don't we want to check whether it's really room temperature? There we go.

[00:21:48]So, let's have a look.

[00:21:53]We've also got a thermal imaging camera on the go.

[00:21:58]>> 21 and a half degrees of our gin and vermouth. So, a classic uh martini.

[00:22:07]Depending on how dry you like it, the the vermouth is offsetting the gin. You can of course add a twist of uh lemon.

[00:22:15]Some people like a little bit of pickle.

[00:22:17]If you like it dirty, a little bit of olive brine can go in there. Uh, absolutely fantastic. But ultimately 21° and a half, David.

[00:22:28]>> So, what are you going to do? Do you like it um on ice? Do you like shaken or mixed?

[00:22:35]>> Shaken. Oh, okay. Shaken. What's the temperature of the ice?

[00:22:39]>> Temperature of the ice is uh >> this is ice and water. So, what's the temperature?

[00:22:44]zero >> uh 0.2 0.1 like we'll take it. Right. That's a tolerance we're happy with.

[00:22:52]>> Close enough to zero. Okay. So, we're going to mix them together, right? And shake them.

[00:22:57]>> So, >> what's the temperature going to be when we shake the the room temperature? What do you think?

[00:23:04]>> It's going to increase, right?

[00:23:07]>> Because the ice is at zero and the alcohol's at room temperature be somewhere in between, right? Anybody want Anybody want to guess what it >> I'm not Tom Cruz load of ice and then we shake.

[00:23:32]Somebody's still shaking on the back there. That's great. Great work. Great work.

[00:23:36]Now, as we shake, you begin to see and I begin to feel just how cold the shaker gets. You can see some condensation on the outside. You give it a good shake.

[00:23:45]Now, if you're a bartender and you're good at this, 20, 30 seconds, you end up with a shaken martini for us. What's the temperature? We go in and we now register -4 -4 -4 -4 We've cooled the ice. We've made the ice colder.

[00:24:19]What's going on?

[00:24:21]You don't believe it?

[00:24:23]Well, I'm going to try it and make sure that it's okay.

[00:24:28]Actually, what's happening is the same thing for the same reason we added salt to the ice.

[00:24:35]You're trying to make the ice and the alcohol at the same temperature. When it's water, it's at the same temperature. The water and the ice are at 0 degrees, but alcohol melts at a lower temperature. So, it's trying to cool and it can actually cool the ice.

[00:24:54]It brings the temperature of the ice down and so you get something even colder. So, you can actually cool just by mixing them together.

[00:25:09]It is a Saturday after all, David.

[00:25:12]>> Cheers. Cheers to the science of cooking.