Creating ice cream that will re-freeze time after time but still remains as tasty as the day it was made, is a major culinary conundrum. New ways of conjuring up this faultless cuisine may come from the most unlikely places - serving up the perfect ice cream may depend on understanding how Arctic fishes stop themselves from freezing in their icy homes. But if we can mimic this seemingly magical feat, could we do far more than make the perfect raspberry ripple? Could we cryogenically freeze your granny and then defrost her back to her radiant self again?

Professor Tony Ryan
[Tony comes down the stairs of the lecture theatre and hands out ice creams.] Pass one down.
Hello.
I bet you all like ice creams as much as I do.

Do you want a napkin to go with it?
No.
Do you want to give it me back?
OK, how about you, do you want an ice cream?
You have a napkin.

You see, the only reason we can make this delicious treat is that we know some fantastic physics and chemistry.

Chemistry that allows us to make ice cream cheaply and in large quantities and most importantly with great taste and today we're going to explore the science behind ice cream and I'm going to show you how the very same science might save lives in the future.

So to find out what ice cream is made from - I need two volunteers.

You sir, you, yeah, you and the person next to you, down you come.
[Boys stand with Tony in front of table.]
So I'd like you to stand here and you come round this side.
OK, so what do you think the ingredients of ice cream are?

Volunteer
Ice cream.

Professor Tony Ryan
Ice cream.
What's in ice cream?

Volunteer
Flavours.

Professor Tony Ryan
Flavours, OK, what else?

Volunteer
Ice.

Professor Tony Ryan
Ice, very good!
And erm, why is it called ice cream? [Laughter.]
Because it's got cream in it, OK.

[Tony assembles ingredients.] So here's some ice, right and here's some cream.
Actually you find that as well as cream it's got some fat, right, there's something else you've missed out, it's got flavour.

Here's some vanilla flavour, because we like vanilla ice cream, yeah.

Now, does it taste sweet?

Volunteer
Um, yes.

Professor Tony Ryan
Right, OK, that's because it's got sugar in it, OK.
So what we're going to do is we're going to put the ingredients in here, if I can.

Right, so there's some ice, there's some sugar.
Here goes some flavour.
Have you ever made ice cream like this before?

Volunteer
No.

Professor Tony Ryan
No.
Just come round here for me, will you.
There you go, and you, well done.
This is a little bit of cream, yeah.
And we'll just put a little bit, because it's not very thick cream this, so we'll just put a little bit extra fat in there, because actually by weight ice cream's ten per cent sugar, thirty per cent fat and sixty per cent ice cream.

And then what we need to do is give it a good old ...

[Shot of blender.] Ooh, have I broke it?
No, it's working again.
OK, so all the ingredients are there.
Are you looking forward to tasting it?

Volunteer
No

Professor Tony Ryan
[Laughs/audience laughter.]
Really?
I mean it looks like ice cream.
[Boy looks at container of 'ice cream'.]
Have a taste, just tell me what it tastes like, because it's got all the right ingredients, hasn't it.
You have a taste.
Do you want me to have a taste as well?
Go on then, oh, go on, I'll have a taste.

What's wrong with it?
It's fantastic!
So thank you very much for being so good at that.
Ugh, it's horrible!
[Applause.]

[Overhead screen shots of icebergs.] Now ice is found all across the planet, even at the Equator and we have icebergs floating on the sea.
Why do they float?

You see, ice shouldn't float, should it?
It's a solid and solids are supposed to be denser than the liquids.
So here's an ice molecule, it's actually a water molecule and when the water molecules pack together, they go from being a beaker of water, like this, to being an ice crystal, like this.

You see the water in the liquid is all mixed up and random.

And the molecules are actually closer together and when it becomes a solid, the molecules go further apart, because they have these things called hydrogen bonds that make them expand a little bit and our friends at St. Wilfred's school helped us to demonstrate this.

[The overhead screen shows footage of children lying down 'acting' as hydrogen atoms and bonds.]
In this demonstration their legs are the hydrogen atoms and their arms are the hydrogen bonds.
So when they crystallise, and arm grabs hold of a leg and you get a lattice of evenly spaced out molecules and this is a clue as to why the ice floats.
So out they come again to make the crystal.

So we have, under the microscope and Mike Hamslow from our chemical and process engineering department's going to come down and run it, a cold chamber.

You see, when the water's in a liquid, it's buzzing around and they're moving and they hit a surface.
Sometimes they stick, sometimes they come off and eventually they stick and the crystal grows.

So Mike, is it crystallising yet?

Mike
Tony, it is.

Professor Tony Ryan
[Overhead screen shows growing crystals.]
Marvellous, let's have a look.
Oh, oh it is just starting to crystallise now.
So you can see the crystals growing.
We have them on the end of a needle so you can see them under this microscope.
We can control the size of an ice crystal by how fast we freeze the water, so the point of this needle was acting as a surface to nucleate, to cause them to be born.

Thanks Mike.

Mike
You're welcome.

Professor Tony Ryan
Cheers. [Applause.]

So if you cool the water very quickly, you form lots of ice crystals on lots of surfaces.
Any speck of dust or bubble will be there to cause crystals to grow and eventually there'll be no more free water molecules buzzing around to add onto the crystal.
So if we want to make perfect ice cream, we need to know how to cool the ingredients quickly, because what we want to happen is that the molecules rattle around and make a lattice.

[Close-up shot on screen of water molecules.]
So here are the water molecules on your screen now.
They're rattling around, we slow them down as they cool and eventually they'll lock into place and we need to lock them into place in lots and lots of small crystals.

So now, to make our own ice cream, I need a couple more volunteers!

OK, we'll take this person here and the one in the pink jumper behind her.

You two are going to form part of a production line with Annie and you're going to mix things together.

[The volunteers stand with Annie by a bowl.]
She'll show you what to mix together and then we'll pass them out into the audience.

So, they're going, they have pre-made ice cream ingredients.
They're going to put them in a big bag along with some water, some ice and some salt and then we're going to pass them out to you and you're just going to squidge them gently, otherwise you'll have cold, wet feet, right and we're going to make ice cream.

So we can't be sure when and where ice cream was invented, but we're going to use a technique that people have used for well over a thousand years.

[Close-up shot of container and thermometer.]
So here I have not quite ice and water and the temperature should read, what?
What should the temperature be?

Shout.
[Minus, what, nought degrees].
Nought degrees and it's not quite nought degrees, because the thermometer's in a little bit of air, right, so what I'm going to do is I'm going to put some of this ice into a bag - right and then I'm going to just add a touch of water, because nought degrees is when you have ice and water together.
So - we can't quite get there, so what I'm going to do now is add some salt.

[Shot shows the temperature falling.]
So I've added the salt and look what happens.
The temperature plummets.
It's already down to minus three.
In fact, if I get the amount of salt and ice right, it'll go down to an amazing minus twenty-one degrees.

So that's down to minus six, it's still falling.

So when you pass those bags around, be careful.
They're going to be maybe minus ten, minus fifteen degrees centigrade.

And they might stick to your hand, OK.
So be careful.

So our production line's just about finished.
Let's make this the last bag.

Now whilst those are being passed round we need to find the pouches and the pouches you're going to get look like this and they're going to help us explain why the temperature went down.

So there's a little button in the corner, a little metal disc.
Those of you who've got a pouch, I want you to click the metal disc now and you can see there's a tree-like structure growing out from the pouch.
Is that right?
Can you see it?
Have you clicked the disc, yeah?
We can see tree-like structures. And what else is happening?

It's getting really, really hot.
You see this tree-like structure, these are crystals forming inside the pouch and when they turn from a liquid to a solid, they give out heat and this gives us a clue as to why the temperature fell when I added so much salt.

[Film footage on screen of lorries gritting a road.] So in the winter you see lorries spraying roads and paths with grit.

And the lorries are actually spreading salt on the road.
And the salt melts the ice.
And it melts the ice because on ice there are water molecules that are buzzing off into the water and in the water there are water molecules that are buzzing in to the ice.
But when the salt goes down, the molecules in the water have someone to play with, so they don't want to go on to the ice, they want to stay there, so molecules stop going on to the ice, but keep on coming into the water and the ice melts.

But it needs heat to melt and it takes that heat from the road.
In the same way that my bag of iced water and salt got cold, it got to minus seven degrees centigrade.
So, now we've seen if you want to make ice cream you need to have exactly the right ingredients and the right conditions.

To get an ideal ice cream, you need the right texture.Small crystals, so it feels good in your mouth and in a minute we'll look at how texture alone doesn't control our perception and our enjoyment of food.

Professor Tony Ryan
[Tony places potatoes into electric chip fryer.] So we've seen how important texture is in our enjoyment of food.

But a number of other things dictate how we perceive food.
What we experience is actually a combination of chemistry, physiology and psychology.
And it depends on a blend of clues or sensations.
Texture, look and smell.
But we have a very simple way of changing all these sensations and that's called cooking.

You see, all cooking is chemistry.
But not all chemistry is cooking. [Laughter.]

Flavour, taste, texture and appearance can be modified by cooking.
So let's look at the commonest way we cook and that's using heat.

[Tony holds up steak and potato.] So you always get told you are what you eat.
And in my case, that's some of this steak and some of these, potatoes.

Fats, carbohydrates and proteins.
And they're all made of polymer chains, long molecules, carbohydrates and many sugars joined together, proteins and many amino acids joined together.

Carbohydrates keep the potato rigid.
Whereas proteins make muscles.
And some of these bonds are broken down by the heat.

So, when we cook we release sugar from the carbohydrate and we release amino acids from the proteins.
So let's have a look at how these are doing.

Just give them a shake.
Oh, they look ready. [Laughter.]

That lid always does that.

So, now I need a volunteer to taste some chips.
And I thought this might be a popular demo.
Now Jamie here has a microphone on, because I need to talk to him.
So I'm very sorry, down you come, Jamie.

But don't worry everyone.
Jamie, can you taste this chip for me? [Laughter.]

[Jamie bites into raw potato 'chip'.]
Just have a bite, tell me what it's like.
Chew, chew, if you don't like it, you can spit it out on one of these napkins, you don't have to ... [Laughter.]

So, what was that like?

Jamie
Chewy.

Professor Tony Ryan
Chewy.
It was hard, wasn't it?

Jamie
Yes, quite hard.

Professor Tony Ryan
And did it taste floury?

Jamie
Yeah, it was ...

Professor Tony Ryan
Did it make the inside of your mouth dry?

Jamie
Yeah.

Professor Tony Ryan
You see, we don't often eat raw potato, do we? [Laughter.]

And that's the reason why.
So would you like one of these, be careful, they might be hot. [Jamie takes a cooked chip.]
Give it a blow.
You see, these are not so rigid.
They're soft on the inside and they've changed colour.
How nice is this?

Jamie
Mmm.

Professor Tony Ryan
Pretty good, aren't they?
I'll tell you what, Jamie, you have another one [thank you] and thank you very much indeed. [Applause.]

[Tony holds up a cooked chip.] Some very important things have happened. The texture's gone from hard to soft. And they've been coloured.

And sugars have been released so they taste sweet, here you go, would you like a chip?
Be careful, make sure you blow, because they're rather hot. [Thank you].
They're hot, don't burn yourselves.
But we can't put all the changes in taste between a raw chip and a cooked chip just down to the break-up of the carbohydrate or down to the break-up of the amino acids.

You see, when these break up, the carbohydrate releases sugar and the protein releases an amino acid and these can react to produce a bewildering array of flavours.

They also produce taste and they also produce colours.

[Tony holds up a crisp packet.] So much so, that this famous brand of roast chicken flavoured crisps [laughter] are suitable for vegetarians. [Laughter.]

How does that work?
Do chickens grow on trees? [Laughter.]

I think not!
You see the flavour molecules that give us roast chicken are made from two amino acids and one sugar, so you don't need to take them from a chicken at all to get that same flavour molecule.

So we've seen how cooking affects taste.
Let's see how other things affect our perceptions.
Let's start with colour.

So I want some volunteers to help me.
We'll take this person here with her hand held firmly in the air and the person next to her, perhaps and this young man who's pointing to himself.

If you just want to line up here.

So do you want to start pouring the others.

[Volunteers stand round table/drink tasting session.] First I want you to take drink, taste drink 'a' and then we'll taste drink 'b' - but just hand your finished drinks, or your not quite finished drinks to Annie.

So there's drink 'b' - OK, have a taste of that.OK, and now finally, drink 'c' - which one do you prefer?

'C' - definitely 'c' - you prefer 'a' and you prefer 'a' - right, OK. [Laughter.]

Well what I want to do is I want to blindfold one of you, send the other two back to their seats and see if you can tell which one, which one's which.
Now I think you expressed the strongest preference, so we'll keep you here, thank the other two very much.

What I want you to do is put this blindfold on.
And then I'm going to ask you to taste the drinks.
And because you preferred one drink, you should be able to recognise it, right? [Mmm].

[Blindfolded girl tastes liquid.] So what colour's this one? [Blue].Right and what colour's this one? [Clear].

[Brown].
And this one.[Pink] ...
[Laughter/applause.]

Take your blindfold off.
You see the last answer summed everything up.
What you expect to taste depends on the colour.
So this young lady expressed a preference for the brown drink because they were all cola drinks and they all tasted the same.
That's why she couldn't tell, and said pink.
So thank you very much indeed. [Applause.]

You see, the difference is psychological.
It's something that humans have been aware of for a long time. That's why we have the power to breed plants of different colours.
We can pick and choose the colour of our food by breeding or when we cook by adding extra colour, or when we make drinks by colouring the drinks.
So we've seen that sight and especially colour is very important, so let's try to see how important taste is.

And I have a young man up here who's already volunteered.
What's your name? [Alex].

All right Alex, pleased to meet you [pleased to meet you].
Do you just want to stand here in front of this trolley, yeah.
Before you put the blindfold on, I want you to put a nose clip on, OK [OK], so put the nose clip on, right and then the blindfold and then I want you to stick your tongue out.

Now you can't peep underneath those blindfolds, can you?
I don't want any peeping, OK.
So I'm going to put something on your tongue, but it won't hurt at all.
[Tony places a piece of food in the boy's mouth.]
I just want you to guess, if you can, what it is.
OK, so tongue out.
Don't chew it, whatever you do, just leave it on your tongue.
Have you chewed it? Good man, what do you think it is?

Can you say?

Volunteer
I have no idea.

Professor Tony Ryan
You have no idea. [Laughter.]

Well, I tell you what, I'm going to help you by taking your nose clip off and see if you can tell me what it is now.
What is it?
Can you tell?

You don't like it, do you.
Do you want to spit it out?

Volunteer
Erm, OK. [Laughter.]

Professor Tony Ryan
What was it?
Take your blindfold off.

Volunteer
Oh!

Professor Tony Ryan
Did it taste like onion?

Volunteer

No, not at all.
And it didn't ... it didn't quite taste like onion ...

Professor Tony Ryan
So you had apple in your mouth and what I expected to happen was when I held the onion under your nose, you'd say that this piece of apple was an onion.
Do you have a cold? [Laughter.]

Volunteer
No, no - I don't have a cold.

Professor Tony Ryan
Oh well, thanks a lot. [Laughter/applause.]

Professor Tony Ryan
So, what was the nose clip doing?
Well the nose clip was taking away his sense of smell.
And the chemistry and biology of smell is very, very subtle, because your tongue kind of lets you feel things.
It give you some basic taste, but it doesn't have aroma.
[Demonstration using model of head cut in half/showing appropriate organs.]
You see, what happens is all the action in terms of how you experience food, taste, flavour, aroma, goes on in here and there are receptors and those receptors detect special molecules that say, this is an apple, this is an onion - and it's linked via a tube at the back of your mouth up to your nose, so when you chew, mashing your food up, you release those flavours, those flavour compounds.

And they travel up the tube and are detected by the receptors in your nose.
[Overhead screen shot showing silhouette of a man chewing food.]
So this guy's chewing away, yeah, his dentures are going up and down - [laughter] - you see, we all have two thousand receptors, or we could have and they detect two thousand different aromas.
But the nature, but nature and chemistry have combined to make things really quite complicated.

So, I gave you all an envelope on the way in and now's the time to use it.
So I hope you've got something left in your envelope.

In there you'll find a seed and a sweet.
I want you to try the seed first.

[Audience reaction.]

Now, the seed first, have you tried the seed?

What is it? [Caraway].
Caraway, very good, it's caraway.
Now you can put the sweet in if you don't like caraway.
And what about, what about the sweet?
No, it's not soft mint, it's spearmint.
Thank you very much indeed.
You see the sweet's a spearmint and the seed's a caraway seed and they both taste completely different, but the flavour is the same compound, it's a compound called karvone. So - I have a karvone molecule here and karvone molecules are really rather lucky, because they have a twin, but they're not identical twins, they're mirror images, these two molecules.

[Demonstration of molecule and mirror image.]
So here's the karvone molecule and here is its mirror image. Can you see it?
So if I lift it up, out comes its mirror image, you see, they're reflected in the mirror.
I can't put them on top of each other, because the bits are in the wrong way.
So, if these are up your nose, yeah, they go to their own receptors, so out comes the receptor.

Here's karvone big brother, all right, so - and this karvone molecule won't fit in the receptor, right.

But this karvone molecule, because you're chewing a spearmint, goes - plop - in it goes.
You see, if you hit the right receptor, you get the right flavour and there are thousands of receptors for thousands of different flavours and we don't all have all of them.
So we all detect different smells from the cocktail that's released in our food.

Hence, not everyone likes the same food.
So when we say something tastes great, we're actually making a value judgement based on a wide variety of sensory information.
But we can manipulate our food and change its taste and texture and armed with this knowledge, we will be making the perfect ice cream in a few moments.

[Applause.]

So, making the perfect ice cream.
Let's have a look at what we already know.
Ice cream's a mixture of sugar, fat and air held together by ice crystals - ice crystals that we know have to be small.
So we need a way of making them and keeping them small and hopefully this should have happened with our ice cream.
So this is one of the bags you were passing around earlier and let's see, mmm, delicious.
You make great ice cream.

You see we used the ice and the salt and got down to about minus ten degrees, and how did we keep the crystals small?
Well we kept them small by you squidging them and if you were doing this at home, making ice cream at home, what you'd do is, you'd put the mixture in the freezer, then you'd lift it out and you'd mash it with a fork, or if you were really rich and lazy, you'd have an ice cream making machine.

[Film footage showing ice cream making procedure.]
But how do you think they make ice cream in the ice cream factory?
Well at first glance, it looks totally different but it's really very similar.
You see you're only seeing the end here.
Before this, there was a large vat and the large vat was cooled down with a very cold liquid, called liquid ammonia and small ice crystals formed on the side of the vat and they were scraped off, so no large crystals get to form and the ice cream that leaves the factory is just like that we've made in the bag.
It's a perfect mixture with only small crystals.

But if you take too long getting home from the supermarket and it defrosts and you stick it back in the freezer, you know what happens, don't you.
It goes all hard and gritty around the outside and it's difficult to get out, because it's re-frozen and it's re-frozen in your freezer and that'll only freeze it slowly.
Consequently you get big crystals.
So controlling the crystal size and shape is really important, regardless of the speed we freeze it at.
So if you can control the size and shape of the crystals, you can reach the holy grail of ice cream production.

You can make liquid ice cream and transport it as a liquid and even take it home from the supermarket as a liquid and then put it in your freezer and it makes perfect ice cream time and time again.
And here maybe nature can help us.

[Tony compares crispy lettuce and defrosted frozen lettuce.]
You see, most plants can't cope with extreme cold.
Look what happens to this nice, crispy lettuce if we freeze it and then let it defrost.
It becomes this soggy mush.
So why is this?
Well we saw earlier, when you freeze water, it expands and the cells are full of water, so the cells have to expand - and you saw under the microscope that the crystals are rather pointy and they poke holes in the walls of the cells. Consequently we get mush.

You see, all plants and animals are made up of water filled cells and yet there are many, many species that live in very cold climates.

[Penguin is brought into lecture theatre.]
Here's Percy the penguin.
He's a Humbolt penguin.
Hey up, Percy, where are you going? [Laughter.]

And he's not very easy to control.
So there's Percy the penguin.
He comes from the South Atlantic ... Chile and Peru and sometimes it gets well below zero and he's very well adapted to live in these cold climates. He's warm-blooded and he can control how much blood he sends to his feet.

[Percy follows Tony round lecture theatre.]
You see - [laughter] - Percy ... he likes me, but we'll have to get him off.
Come on ... [Laughter.]

Pick him up.

You see, many animals who live in polar regions, like Percy's relations - has he not gone yet, that penguin?

Many animals who live in polar regions, like fish and even amphibians, they aren't warm-blooded.
They can't control how much blood they send to their feet.

But how do they survive, surrounded by ice??
They should freeze or burst.
[Trolley with container of frogs is wheeled in.]
Well, these are some frogs. They live in the north of Canada where it's very, very cold and when ice forms on the skin of the frog and here's some that are frozen, it stimulates a chain of events in every cell in the body.

What the frogs do is they move glucose into the cells.
And the glucose acts like an anti-freeze.
It makes ice crystals grow at lower temperatures.

Just like we saw when we added salt to ice and the temperature went down.
These cells also secrete anti-freeze proteins, so the glucose takes the freezing point down and there are then these special proteins that stop the ice crystals growing, preventing them from bursting the frog's cells.
And to show you how they work, I'm going to need six volunteers.
Now, I've got to use the party hats, up near the back.

We'll have these two here and we need one more and we'll take this person here.
So now, party hat number one, right at the front.
Party hat number two, behind her, to one side, behind her, to one side, nice and close, shoulder to shoulder, you two.

Then you three line up, shoulder to shoulder, right.
Now you're going to play the part of the water molecules.
You formed already an ice crystal and you're inside the frog.
Now I want you to hold on to this.
Hold on to it tightly, just there for the moment.
So this is the antifreeze protein.
[Group are wrapped up with 'antifreeze protein'.]
And what it's doing is it's wrapping you up, OK, so round and round it goes, OK and so you're all wrapped up.

Just tuck that in there, hold it there.
Now, what happens when a water molecule comes along?
Now the water molecules use their hands, don't they, to make the hydrogen bonds.
But there's no legs or arms for the water molecule to grow onto.
So this crystal can't grow.

It stays small.
And that's how these special proteins work.
And they control the size of ice crystals.

Right, out you get.
I'll help, let go. Let's unravel.
Thank you very much indeed, all of you.

Professor Tony Ryan
So as the freezing process progresses through the veins, two thirds of the water in the frogs' bodies turn to ice.
[Sequence with rotating footage of frog in suspended animation.]
But there's hardly any damage done to its cells, because they're all locked up.
The ice makes the frog go into suspended animation, just like the frog that came out that was frozen.
And the miraculous thing is that the cells suddenly change the way they work.

You see, cells in bodies like ours, coordinate their actions, working together.
But when the frog freezes, its cells, they stop collaborating.
They don't work together any more, they just keep themselves alive.

[Film footage of frog emerging from suspended animation.]
But when spring comes, they know exactly how to reconnect. They know how to make a fully functional frog again.

It's as if we disconnected every telephone in the country and then we rewired the exchange and everyone's phone worked first time.
That would be amazing, wouldn't it!
And this gives hope to the followers of cryonics.

You see we could replicate this freezing process in human bodies, freezing them, let's say, in liquid nitrogen, then bringing them back to life again, we could fulfil that dream.
You could freeze your granny before you lost her to some currently incurable disease and then defrost her when a cure is discovered, so that you can make her better again.
Well let's say that we could preserve a human heart.
You see, outside the body, the shelf life of a human heart is only four hours.

Transplants have all sorts of problems. You see we can't preserve organs.
We can do cells, we can do thin sections.
But if you're going to preserve an organ you have to freeze it all very quickly before it starts to die.

You see, the technology to freeze thin sections of cells has been around for many, many years and we've been freezing blood vessels, skin, intestines, blood, but organs are very different.
You see, this heart, don't worry, it's not a human heart.

This is a pig's heart and it's rather complex.
It's a layer of many, many kinds of tissues.
[Close-up shot of the heart being dipped into liquid nitrogen container.]
So if I try and freeze it quickly by dunking it into liquid nitrogen, it really does freeze quickly. This stuff's at minus a hundred and ninety six degrees centigrade.
So you can see it's frozen, right.

[Tony chops heart open with meat cleaver.]
But when I lift it out, I can - chop it open and it's still rather rare inside. [Laughter.]

You see, we've not sucked the heat out fast enough.
Whilst the cells on the outside had frozen, the cells on the inside could be dying.
[Close-up shot of Tony pulling out heart from liquid nitrogen container.]
But what about when the, even if we could freeze the whole heart, this is a whole heart now.
Look what's happened already.
It's already split.

[Shot of heart shattering.]
I only have to give this the gentlest of taps and it absolutely shatters - and even if we didn't have this problem, when we defrost one, look how it's turned a rather unpleasant shade of grey.
[Shot of defrosted heart in dish.]
Right, it's gone all mushy on the outside, just like the lettuce went mushy on the inside.

So, we need to find a way of regulating these ice forms and you can appreciate why I want to wash my hands, can't you.

You see if we could control that freezing process, preserving cells, we could start to save lives.
Now, if you could freeze a heart and then transplant it, there wouldn't be that little four hour gap.
We could help lots and lots more people and maybe we could use the anti-freeze proteins that are in frogs, to help us.
We would be able to coordinate the freezing process and get them to defrost altogether, but I really think that we might be studying the wood frog for quite some time.

It may be a while before we can freeze organs, but the scientists are looking to use these antifreeze proteins in a totally different and more accessible way.
We could make the ultimate ice cream free from large gritty crystals, right?

And save all that money in transport costs, by transporting things at room temperature rather than being refrigerated.

Now all these things are a while away, but one thing we can do here and now, is we can make ice cream in seconds.
So I'm going to make an attempt at the world ice cream making record, to make the fastest ice cream in the world.

[Demonstration/ice cream making sequence.]
And Sarah Buckley, who's an ice cream scientist is going to help me out.
Professor Mike Hanslow, who you saw operating the microscope earlier, is going to be an independent timer - and just to ensure we have made ice cream, we even have a fully qualified chef, OK.

So, the rules are quite precise.
All the ingredients have to be at room temperature, with the exception of the liquid nitrogen, because that has to be at minus a hundred and ninety six.

So, you need to count me in. Five [four, three, two, one - go!]

[Clock on right-hand side of screen records ice cream making process.]

Oh, ice cream [yeah] done.

[Applause.]

The last record I held was for the hundred metres at high school.
The previous record was fifty-four [fifty-four point five seconds].
Right, and we did it in thirty-six point o five!

[Applause.]

So now, all I have to do - do you want to get some out for me, Sarah?
Is I want the front row to come down, one by one.
First up is Maria Ryan, my daughter, have a go, Maria, how's that?
[Maria tries ice cream.]
Is it cold?
Is it nice? No? [Laughter.]

I'm going to have to have a word with her grand-dad, he told her to say that!
Come on, the rest of you come down.
Come on Daniel, down you come, Rachel, Emily.
Come back Maria, come on, have a taste, it's all there, let's have a go, come on, come on here.

You see, what I wanted you to see from this series of lectures is that everything around us isn't as simple as it first seems.

So next time you're in the supermarket, don't just look at the brands.
Marvel the molecules inside.
And when you're in the garden, remember that the spider knows more about designing materials than we ever will.

And on the motorway, think about the tyres in contact with the road, the tyres that'll keep you safe.

Just take a moment to review the world around us, explore the materials and how they got there.

You see, you are surrounded by smart stuff.

[Applause/music/credits roll.]