A Matter of Taste The Secrets of Your Food

How often do you stop and really think about your food?

Look at all this lovely fat and sugar. Yummy.

Do you ever wonder why you eat what you eat,

what cooking does to food...

Delicious.

..or what effect it has on your body?

I trained as a medical doctor

and I'm absolutely obsessed by nutrition

and the hidden chemistry of food.

So, I've teamed up with botanist James Wong to explore food,

each of us coming from very different perspectives.

Truly delicious.

Together, we have taken over

the country's leading food science lab...

..to deconstruct some of our favourite foods...

It's all sunk to the bottom.

..and to reveal some truly remarkable secrets.

I want to find out what effect food has on us and our biology,

right down to the molecular level.

As a botanist, I am fascinated

by the massive diversity of edible plants on our planet.

I'm going to put them under the microscope

to discover exactly how their biology interacts with our own.

So, join us, as we seek out

the most remarkable food stories on the planet

and reveal the hidden science of our food.

Flavour makes our food delicious.

Each flavour is a potent combination of aroma and taste molecules.

Get that combination right and food tastes heavenly.

But what is taste?

Thai cuisine is particularly good

at exciting our full range of taste receptors...

..on one plate.

So, this is a Thai stir-fry and I'm very fond of Thai.

There is...

..a bit of fried chicken, lemon, garlic,

onion - a real sort of explosion of taste.

And it's really strange to think that all these sensations

which are going on in my mouth at the moment

are generated by five simple tastes.

'In front of me, I've got liquids containing chemicals

'that will trigger these different tastes.

'I have no idea which is which.'

Salty. That's definitely salty.

Sweet.

That is sort of bitter, a bit like coffee. And this...

..is similar but more lemony and makes your mouth pucker up.

This is sour.

And this one is really hard to describe.

This is the taste that has been most recently discovered.

This is umami.

The word "umami" is a derivation

of the Japanese for "a pleasant, savoury taste".

And it is very, very strange to think that every taste sensation

you ever have will consist of one or more of these tastes.

The sensations happen here, on the surface of the tongue.

Our tongue holds around 4,000 taste buds.

Inside them are the five taste receptors.

In humans, this is where the taste begins

and in this programme, we'll show you how the food we eat

dazzles each of these receptors.

But why these five tastes?

And why is it that some combinations taste vile

and some taste utterly delicious?

'We're going to travel the globe, in search of the foods

'that are particularly good at stimulating each taste...'

JAMES LAUGHS

..and in the process,

uncover how evolution underpins our relationship with food.

To learn about the most unusual taste,

I've come to an extraordinary celebration

of our most popular fruit, which is rich in umami.

CROWD HUBBUB

I'm here, in southern Spain,

with about 20,000 other people to celebrate the tomato.

CROWD HUBBUB

THEY CHANT IN SPANISH

Welcome to La Tomatina and the world's biggest food fight.

It's been running for over 70 years

and it's thought it started with a street fight.

It was so much fun,

the locals decided to do it again the next year and the next.

As well as making a perfect food missile,

tomatoes carry a heavy punch of umami.

The trouble with being at the back is you get hit a lot.

But what exactly is umami

and why does it have such a powerful hold over us?

The answer lies inside the tomatoes.

'To get at the umami, I'm going to blitz them,

'then spin them at high speed in a centrifuge,

'filter, then finally stir and simmer to concentrate the taste.'

After all that boiling down, this is all that's left

and it no longer smells tomatoey at all

because those volatile flavours have been boiled off.

And this stuff...

..doesn't taste tomatoey either.

It tastes salty, earthy, meaty.

What my tongue is sensing is a chemical known as glutamate.

It's an amino acid,

a type of molecule derived from protein in the tomato.

Whenever you get a glutamate molecule in food,

it triggers that umami taste,

fuelling a desire for more umami-rich food.

It's our love of the glutamate in tomatoes

that has made them such an important crop for this region.

HORN BLARES

BELL TOLLS

It's found here, in the ancient oak forests of south-west Spain...

..home of the chunky local pig known as the "pata negra".

These pigs roam freely, foraging whatever they can find.

But their favourite treats are the acorns

that fall from the oaks every winter.

And it turns out that pigs and acorns are a match made in heaven.

Together, they make the most delicious and most expensive

umami-packed ham in the world - Iberico ham.

HEN CLUCKS

It's early morning in January.

Acorn season is coming to an end and Juana Marquez is preparing

for one of the most important events of her year.

In this part of Spain, the annual killing of a pig is a major event.

It is known as a "matanza",

and it involves the gathering of an entire family.

THEY SPEAK IN SPANISH

PIG SQUEALS

For Juana's pig, it's as respectful a death as you could hope for.

It will take the family the entire day to turn 150 kilos of pig

into enough meat to keep them going all the year.

But butchering is only the prelude to transforming this meat

into an incredibly powerful umami-tasting explosion.

The secret to the intense umami taste begins

with the extraordinarily thick layer of fat...

..which comes from the acorns the pigs enjoyed in life.

The acorn fat from the local oak trees is rich in oleic acid,

the same fatty acid that's found in olives.

That's why the locals refer to the pigs as "olives with legs".

Walking olives that can eat up to ten kilos of acorns a day.

Most hams end up here, in the darkness of an Iberian cellar.

This is where biochemistry kicks in and the exquisite umami taste forms.

The surface of the ham is under constant attack.

Microbes and oxygen in the air react with the fat on the outside,

making it yellow and rancid.

But the meat within is protected.

The acorn-fed fat layer is so thick it can keep the meat air-free

for up to three years, much longer than any other ham.

This allows the natural chemistry locked inside the flesh to unfold.

The meat starts to cure.

Over the years, naturally occurring enzymes

break the proteins in the meat down

into their basic building blocks - amino acids.

One of these is the all-important glutamate,

the molecule responsible for the taste of umami.

The longer meat cures, the greater the build-up of the glutamate

and the stronger the taste will become.

And time is exactly what its thick, fatty case provides each ham.

By the end, these hams have 50 times

the glutamate levels of fresh meat...

HE PLAYS GUITAR

..making them the world's finest, meatiest,

most delicious umami-tasting hams.

It's a taste prized by charcuterie connoisseurs the world over.

But there's a biological reason

why we are drawn to the umami flavour of glutamate.

So, the reason... Mm!

..why this ham is so delicious

is because glutamate is one of the building blocks of protein.

And protein is essential to the building

and running of every cell in our bodies.

THEY SING IN SPANISH

So, what the ham is really saying to me is,

"Eat me because I will make you big and strong."

THEY SING IN SPANISH

And the way it sends that message is, of course, via my taste buds.

As food enters the mouth, it meets the tongue,

a seething landscape of muscle, covered by spiky papillae.

These help move each mouthful of food around.

As it swirls across the tongue, the food comes across larger,

dome-shape papillae, and here, we find the taste buds.

The glutamate enters each bud,

where it encounters the five taste receptors.

But the glutamate molecule has a distinctive shape

that can only activate the umami receptor...

..sending a signal to the brain that tells us,

"Mm, that mouthful of food is rather delicious."

We're hardwired to enjoy the taste of umami

because it signals the protein we need to build our bodies.

But we can't survive on protein alone.

We would grind to a halt without a ready supply of energy.

So, we have another taste receptor

that fires off whenever it encounters the chemicals

that give us a quick energy hit.

Yum!

When you bite into a strawberry,

if you had to pick one word to describe its taste,

you would probably pick "sweet",

and that's how our bodies detect the amount of sugar that's in fruit.

'But sugar and nature seldom comes on its own.

'It's usually balanced out by another taste -

'the taste of acid.'

I'm going to show you that,

with a fantastically geeky piece of kit here.

This is a pH meter and it detects how acid solutions are.

Now, I've got some distilled water here.

OK.

And pretty much instantly, bam.

As I was hoping for, pH 7.

Perfectly neutral.

On the other end of the scale,

I've got this stuff over here - some hydrochloric acid.

Exactly what I was hoping for. This is pH 1.

You've got pure water on one end, which is 7,

and hydrochloric acid as 1, about as acidic as it gets.

'So, let's test a range of fruit...'

Let's get some of that juice out.

'..to find out where they fit on the scale, starting with a strawberry.'

Yeah, it's going down.

For something most people describe as sweet,

this is pretty acidic stuff.

Look at that. 3.5.

Right there.

'The pH meter is measuring

'the number of hydrogen ions in the fruit,

'which defines the acidity of each sample.

'Take a watermelon.'

Watermelon juice is relatively non-acidic.

5.5, over there.

'These hydrogen ions trigger our sour receptors,

'so the sour, let's say, in orange,

'is actually the taste of acid.'

Unexpected.

3.5 again.

'Last up, grapefruit.'

Huh, 3.52.

So, this is quite odd.

All this fruit is the same pH,

yet people describe strawberries as tasting sweet,

despite having a similar amount of acid.

Strawberries have a cunning ability to hide their acidity,

which begs the question, why produce it in the first place?

The reason is actually down to a beautiful bit of evolution.

Strawberry plants have specifically evolved

this sweet, succulent fruit here to encourage animals to eat them.

And that's because,

when these seeds pass through the digestive tract of an animal,

they're deposited, with a bit of fertiliser, far and wide,

helping the strawberries' empire grow.

The thing is, that only works when the seed is fully mature

and ready to sprout. Until that point, they're not sweet at all.

In fact, they're packed full of acid, making them taste sour.

It's an animal deterrent.

The mild acidic solution from the unripened fruit

washes over the tongue, stimulating the sour receptors.

The brain interprets this taste as unpleasant

and a sign that the food could be spoiled or unfit to eat.

It's a biological reaction that plants use to their own ends.

A taste strong and repellent enough to put most animals off.

'But just at the right moment,'

when the seeds have matured and are ready to grow,

it needs to mask this acidity to make it more palatable.

All the acid is still there,

but the fruit becomes flooded with sugar,

produced when hormones from the seeds announce

they're ready to be eaten.

The sugars react with other plant molecules

and make attractive red pigments that say, "Eat me."

I know you're not supposed to eat them till you've paid, but...

..that's the point. They are irresistible.

So, everyone's happy.

The plant, having sacrificed some sugar, gets its seeds spread...

..and, in return, the diner gets a sugar reward.

But the strawberry is sneaky,

because we may not be getting as much sweet sugar as we think.

I love strawberries and I also love blueberries.

But which has more sugar in it? Well, going on taste alone...

..I'd have said it's the strawberry. But am I right?

What I'm going to do is squeeze a few of these,

get a few drops of juice out.

That's the blueberry done. Now to do a strawberry.

Now I'm going to use this thing, which is called a refractometer.

What happens when light passes through any liquid is it gets bent,

and the more sugar there is in that liquid, the more it gets bent.

First to be tested for sugar is the blueberry juice.

And then I can look at the light and I can see a number.

This gives me the number 13. So, that's 13 for the blueberries.

Let's do it again with the strawberry.

Wow, that's surprising!

Er, that is about 8,

which means it's nearly half as much sugar per gram

as there is in the blueberries. I am genuinely surprised by that.

So, why is it that a strawberry tastes so sweet

but it doesn't actually contain that much sugar?

Well, part of the secret of its success...

HE INHALES ..is its smell.

Surprisingly, strawberries have altered the way they taste

using the power of smell.

Because, alongside the molecules

that give strawberries their characteristic aroma,

there lurk other smells with a more crafty purpose.

36 molecules that seem to boost our taste sensation around sweetness.

The aroma deceives our brain into thinking

we're getting a lot more sugar than we actually are.

Despite the fact that I now know that an awful lot of the sweetness

I think I'm experiencing in my mouth is actually coming from stuff

that's going in nose, it hasn't diminished my pleasure at all.

I still find strawberries deliciously sweet.

It's a clever trick.

By boosting how sweet its fruit seems to be,

the plant needs to give away less sugar,

while still encouraging us to spread its seeds.

Food scientists are really interested in discovering

just how strawberries do what they do,

because if they could replicate that trick with other foods...

..then they could produce stuff which tastes satisfyingly sweet,

but which has far less added sugar.

Our sense of taste is not just about attracting us

to what's good to eat and when.

It's also evolved ways to help us avoid foods that can kill us.

Take the seeds in fruit.

Even a few crushed cherry or plum stones can produce

enough cyanide in the gut to cause paralysis, liver and kidney damage.

Rhubarb leaves contain the same chemical used to make bleach.

And uncooked, just five raw kidney beans

contain enough phytohaemagglutinin

to bring on vomiting, nausea and diarrhoea.

Here, in Peru,

there's an everyday food you might not expect to be a threat.

Eating is a dangerous business.

The world is full of things

that look like they could be interesting to eat.

But some things might not be such a good idea.

Take the potato, for instance. Is it friend or foe?

'The potato plant originated in South America,

'but most of these wild potatoes would have been left well alone

'because of their intensely sharp, bitter taste.'

Potatoes belong to the deadly nightshade family,

which is packed full of species that are super, super toxic.

And a toxin that's found in potatoes is called solanine.

It tastes incredibly bitter. Bad idea to do what I'm doing but...

I barely punctured this with my teeth

and already a bitter bloom is going throughout my mouth

that makes me want to spit it out instantly.

That's my sense of taste telling me instantly,

"This is not good for you. Get rid of it."

Bitter has a crucial role to play in our survival. It's a warning sign.

Your sense of taste is really a complex chemical detector

that allows healthy good-for-you foods in and keeps toxic things out.

The potato plant uses this to protect itself from being eaten.

See all this green blush over the surface?

That's evidence it's started to grow and produce solanine.

They generally are packed in young growing tips

to help protect the plant even more.

So, I'm going to try this sprouted potato and it should be even worse.

Oh, it's... Why did I do that?

Because the consequences of eating a poison can be so deadly,

we have 25 types of bitter receptor, all on the lookout for toxins -

about 20 more than we have for sweet.

Cos sweet is nice, but bitter can be deadly.

Can I spit this out? Sorry.

So, if the original potatoes were poisonous,

how come the humble spud has become such an important part of our diet?

Surprisingly, we have the Inca to thank.

It was in places like here,

in the mountains of the sacred Incan valley,

where the poisonous solanine was gradually bred out.

You know, when people talk about the Inca,

they tend to mention lost cities and temples and gold,

but all of this has nothing to do with power or status.

Everything you see here only exists to grow crops.

And king amongst them? The potato.

But for some people who live on the very edge of existence,

the battle to tame the poisonous spud is still being fought.

Martin Calisaya and his family live here in this village,

4,000 metres high in the Andes.

Their lives depend on the potato.

Almost nothing else will grow at this altitude,

so spuds provide virtually all their nutrition

and they grow a huge variety to survive in this harsh environment.

But even with 100 different varieties,

a hard frost could spell disaster.

As a precaution, they grow the hardiest known potato in the world,

one that can survive even the toughest winter.

The only downside?

They're bitter, poisonous and inedible,

packed full of deadly solanine.

The incredible thing is, the people from the Andes have developed

an ingenious technology that turns poison into dinner.

The trick is to freeze-dry the potatoes

to remove the toxins and so they can be stored for years.

In order to get maximum freeze factor, the Quechua need to find

the very coldest spot and that means going right up there.

Once a year, the Calisaya family haul their crop

of inedible, bitter potatoes to a site

that's 300 metres higher than their village,

ready to begin a food processing technique

that dates back around 2,000 years.

HORSE WHINNIES

At 4,300 metres, we reach the corral,

where the potatoes will be processed.

-BREATHLESSLY:

-Growing potatoes the traditional way

is incredibly labour-intensive.

But here, you've got to haul this stuff up a mountain

and, in this thin air, even just the act of spacing them apart,

so frost gets to them, is killing me.

At night, the temperature plummets.

Ice crystals form throughout the potato, rupturing the cell walls.

This allows the poisonous solanine to leach out.

After a night out in sub-zero temperatures,

these guys are frozen solid.

Up to 80% of the deadly solanine is produced close to the skin,

and the treading process breaks the skins

enough to allow an escape route for the poison.

During the day, when the scorching sun is high in the sky,

the potatoes begin to thaw.

With the cell walls ruptured and the skins broken,

water leaches out, carrying the deadly solanine with it,

leaving a dried, shrivelled product, known as "chuno".

This is it. This is the end result.

And, OK, they might not look irresistible, but this is magic.

In this form, they can be stored for a decade and still be eaten.

It is the ultimate in food security.

So, even if the winter destroys the bulk of their crop,

Martin and his family will be sure to have enough food.

The flavour's great. It's kind of floury, like a chestnut,

like a roasted chestnut, but with kind of smoky, oaky richness to it.

I've got to say...

The Quechua have learnt to outsmart

the incredible bitterness of poisonous potatoes,

and they've also helped all of us enjoy mash and chips.

Thanks to them, nearly all the bitter solanine

has been bred out of the humble spud over hundreds of generations.

Our sense of taste, then,

is far more than just about what we enjoy when we eat.

It's actually a powerful survival mechanism.

Our sense of taste evolved to guide us

through a very different world to the one we live in now.

It was a world where things that tasted sweet were good for us,

because they gave us instant energy,

and where things that were bitter were often bad,

because they might be poisonous.

In the modern world, of course, it's often the other way round.

There's another really important taste,

which is also often confused by the modern world.

It is a taste which is both an invitation and a warning.

It is salt.

We're so used to the taste of salt

that we sometimes forget just how weird it is.

Let me show you something which is really quite surprising.

I'm going to whizz up some coffee.

BLENDER WHIRRS

Bit of boiling water.

I've got a fresh brewed coffee here. Let's give it a go.

And that is really quite...bitter.

'This time, I'm going to add a pinch or two of salt

'to the coffee grounds.'

Let's give it a go.

Now, that's quite strange, because that's very different.

The bitterness has been removed.

It doesn't actually make it pleasanter, I have to say.

It just makes it very different because, oddly, what is happening

is that the sodium in the salt is blocking the bitter receptors.

And so, it really doesn't taste anything like as bitter as it did

which, for me, is a shame because I actually like bitter coffee.

But if you don't, then this is a very neat trick.

And it's this ability to make food more palatable,

more delicious, that gives salt such a powerful hold over us.

And we've also evolved a liking for salt because it's essential to life.

Billions of years ago, life evolved in the oceans.

Exactly HOW it began, no-one knows.

But, as the first simple cells took shape,

they entrapped a little bit of the salty water inside themselves.

Today, every cell in our bodies still carries a little salty water,

a distant echo of our ancient origins in the sea.

Sea water might taste terrible

but the taste of a little bit of salt has this universal appeal.

We like it because we need it.

Salt is vital for life.

This biological need has driven us

to coax salt out of the ocean for thousands of years,

transforming landscapes, like this corner of Brittany.

Over time, this salt marsh has been painstakingly sculpted

into a vast network of evaporation ponds.

Sophie Bonnet-Questiot is one of 250 salt farmers,

each tending to their own network of ponds, called a "salina".

It's the traditional way because it has started in the 9th century.

The technique is really the same.

When the tide is high,

sea water flows 5km from the ocean into a reservoir.

It's then channelled through a patchwork of ponds,

each just slightly lower than the last.

As the water moves down from one pond to the next,

it becomes more concentrated,

until it's ten times as salty as it started.

And then, from the briny water, salt crystals emerge.

I'm collecting very famous salt of Guerande...

..that is crystallising at the bottom of the pond,

directly on clay.

The highly-prized, beautiful, crystalline flakes of salt

contain more moisture than common salt,

which means the taste lingers for much longer.

And being unrefined, other minerals,

like calcium and magnesium chloride,

give it a more complex flavour.

It's the taste of the sea.

And this is it. This is the end result.

After billions of years,

our bodies still rely on the same basic chemistry

that evolved in those first blobs of life in the sea.

Inside the body, salt controls the amount of water in each cell.

Where there's more salt, water will go.

It's a process called osmosis.

It makes cells swell and shrink.

Elsewhere, the sodium in salt is crucial

for the functioning of our nerves.

It's the movement of trillions of sodium ions in our brain

that allows us to think, move and sense the world around us.

And these sodium ions also interfere with our taste buds...

..not just bitter,

but sweet too.

As well as the finest salt,

Brittany is also home to caramel au beurre sale - salted caramel,

that stuff that's taken the world by storm over recent years.

We are hardwired to love sugar and hardwired to love salt, separately.

But when you put them together, something magical happens.

The sodium in a tiny amount of salt actually makes sugar taste sweeter

because, alongside our regular sweet receptors,

we also have some additional receptors that are only activated

when both sugar and salt are present.

So, for the maximum sweet sensation,

seek out the salty taste combinations

found in ice cream, sweets, chocolates and, of course,

in the gooey liquid filling inside a thin French pancake -

a crepe.

It's not polite, but it's delicious.

Salt,

bitter,

sweet,

sour

and umami.

Together, these five tastes form

the foundation of our experience of food.

Because we put food in our mouths,

we tend to think of all the action happening there, on the taste buds.

But, in fact, when we experience food,

we also see it and critically...

HE INHALES DEEPLY ..we smell it.

And it's all of that which adds up to what we call flavour.

COWS MOO

Curiously, flavour isn't just about taste. It's also about the nose.

And around this part of the world,

there's a kind of food that's defined by it's nose - cheese.

Which is odd, because most cheese starts out life the same way,

smelling of almost nothing.

COWS MOO

So, this is where it all begins.

And for someone who's used to knowing

cows on packets in supermarkets,

it's a dose of reality for me.

To make cheese, lactic acid is added to fresh cow's milk

and it's allowed to curdle.

Then the fragile curds are put into moulds where the whey runs off.

-You can take more cheese.

-OK, bigger scoops.

Yes, very good.

'These curds will become the finished cheese,

'but it begins with very little taste and no smell.

'And yet, from this beginning,

'the French produce more than 400 different kinds of cheese...

'..each with their own unique flavour.'

Oh, whoa!

That's intense.

It's like a furry animal.

So, how do all these distinctive cheeses end up being so different?

Well, more than anything else,

the flavour of each cheese is determined by the way it smells.

Take a bit of cheese, cover up your nose,

and even now I can't smell anything, but I can still taste.

This comte, which is normally incredible,

it's kind of like eating a salty candle.

You have this waxy texture, you have a bit of salt,

a bit of bitterness, but it's like eating in black and white.

-HE INHALES

-And it's incredible.

The second you uncover your nose,

this rush of complexity and flavour comes back.

It's like eating in technicolour.

The massive difference between the thousands of different types

of cheese on the planet is all about smell.

This simple experiment reveals the powerful effect

that smell can have on the flavour of food.

'And to better understand how each cheese arrives with its own pong,

'I'm in Burgundy, where they produce one particularly notorious cheese.'

It's the cheese known as the king of cheeses,

Napoleon's favourite and one of the world's smelliest.

There are stories that this stuff smells so bad

that it was actually banned from the Paris Metro.

Nice(!)

'It's a soft rind-washed cow's cheese and it's called Epoisses.

'So, what's responsible for making its uniquely powerful smell?

'For it to develop, the embryonic cheese needs salt,

'it needs time and it needs bacteria.

'Each cheese starts its journey of transformation

'with a specific type of bacteria.

'But it's how these young cheeses are treated next

'that creates their flavour and texture.

'With Epoisses, the rinds are regularly washed

'with water-down pomace brandy, made from the skins, seeds

'and stalks of grapes left after winemaking.'

-It's very fragile.

-Yeah.

-So, you take it slowly.

-OK.

'The brandy imparts some of its own flavour to the cheese

'but, most importantly,

'it affects which bacteria thrive on the cheese.'

One kind of bacteria is called Arthrobacter arilaitensis,

which builds long chain molecules that make the rind go orange.

Another is Brevibacterium linens,

and these break down the proteins in the cheese into smaller molecules,

including stinky, sulphur-based compounds

that give cheese its funky, sweaty aroma.

It's closely related cousin, Brevibacterium epidermidis,

can be found growing on human feet,

giving them THEIR funky, sweaty aroma.

Voila.

Ooh!

They weren't kidding about the way it smells.

It's intense, it's kind of sulphur-like.

It's kind of an instant flashback to the rugby socks

I left in a PE kit once in school for a whole week.

'Volatile aroma molecules from cheese or feet float into the air

'and get sucked up into your nose.

'Each smell compound stimulates a unique combination of receptors

'that allow us to identify the smell.

'In the case of Epoisses, it's the smell of stinky feet

'and it's not particularly pleasant or appetising.

'So why, if it smells so bad, would anyone put it in their mouth?'

But...

..when you eat it, something magical happens.

The aroma compounds are released in your mouth

and they waft up the back of your nose

and they're detected there by the same smell detectors.

But weirdly, your brain perceives them as very different

from if you were to smell forward

and sniff them up the front of your nose.

It's called backward smelling.

Rather than simply smelling the pong,

the brain now combines the smell with the creamy taste

it's experiencing on the tongue at the same time.

This combination of taste and smell

'has a dramatic effect

'on how we perceive a particular odour molecule.

'And for the full effect, always eat the rind,

'since this is where many of the smells lie.'

This stuff...

..no longer is pungent and kind of animalic, like your body.

It's suddenly sharp, garlicky, eggy.

It's just warming, comforting deliciousness.

This is the full flavour experience.

Only by combining taste and backwards smells in our brain,

so we unlock the food's full flavour potential.

Breathe normally in there.

'We may have only five types of taste receptors on our tongue,

'but our noses are packed

'with around 400 different smell detectors.

'I'm testing how good my smell detectors are by sniffing aromas

'extracted from a mystery meal, one of the nation's favourites.'

Whoa, that one's strong.

This one, for some reason, is making me think of wet mackintoshes.

'The twist is, I'm not going to eat even a spoonful.'

Quite aromatic.

'Instead, I'm inhaling wafts of the individual aroma molecules

'that make up this mystery meal.'

It smells almost faecal. I'm trying to work out what it is.

That's weird.

Almost aniseedy.

Smells a damp basement smell.

Not like you can say that's lemon or that's...

..pine cone or...

They're sort of spicy.

'It's only when all the smells are brought together

'at the end of the test that I can finally hazard a guess.'

-Would you like to smell this one?

-OK, yeah.

-Yeah.

Whoa, that's strong.

So, that is definitely curry and it smells like...

-Is that chicken korma?

-Yes, exactly.

We broke down all the aroma components of this curry

and you smell them one after the other.

-And I couldn't put them all together.

-Yeah.

There are many spices so you can get many spicy notes, many meaty notes.

-Some strange notes, like rose, like potato.

-OK, yeah.

-And the pigsty.

-Maybe it was the pigsty I was smelling

-at the beginning.

-Sweaty.

-Yeah.

-Yeah.

Very, very odd, having them as distinctive things

and then trying to add them up to something.

I would never, ever have guessed that was chicken korma.

And yet, when I smell that, I know straightaway it's chicken korma.

-It just smells like it.

-Yep.

It's one of the things I'm quite familiar with. Yeah.

This experiment reveals how our noses help us enjoy food.

Rather than singling out individual notes...

..all the individual aromas come together to form one unified,

instantly identifiable and delicious pong.

Using just 400 different smell receptors...

..our noses are so powerfully tuned,

that it's been estimated we can identify

a trillion different smells.

Like pizza,

roast chicken

or an oak-aged Bordeaux.

In our search for evermore delicious and satisfying things

to indulge our senses,

we've created extraordinary processes

that alter the taste, texture and aroma of our food.

But one has profoundly changed the course of civilisation.

It has transformed our experience and our enjoyment of food.

It is, of course, cooking.

There's evidence our remote ancestors began cooking food

at least 400,000 years ago.

And from the start, they were unwittingly triggering, in our food,

one of the most complex chemical reactions on Earth.

Now, this is a truly wonderful piece of meat.

It's a local speciality, known as "bistecca Fiorentina".

In its raw state, like this... HE INHALES

..it really doesn't smell of anything very much.

But put it on the grill over there,

something truly wondrous will happen.

It's called the Maillard reaction, named after a Frenchman,

but I prefer to call it the "science of the sizzle".

-Fantastic. You don't put salt?

-No, no.

-No?

-No, no.

-Oil?

-No, nothing.

The key to unlocking the flavour in the meat

is the smells that will be generated by the Maillard reaction,

and you can actually see it happening right before your eyes.

So, all this lovely brown stuff you can see over here,

that is the results of the Maillard reaction.

It starts off simply enough.

In the intense heat, the building blocks of protein,

the amino acids,

react with naturally occurring sugars in the meat.

And the beauty of the Maillard reaction is that,

once it kicks off, everything goes completely crazy.

The reaction becomes more and more complex

and intensifies as the products of each reaction

get involved in their own reactions.

Eventually, the whole thing cascades wildly

and generates thousands of different molecules.

Lots of lovely aroma molecules that I am now...

HE INHALES ..hungrily hovering up.

Smells absolutely fantastic now, I have to say.

Complete transformation from that piece of meat, as it was,

-to what it is now.

-Ora, sale grosso.

-Oil.

-OK. Olive oil, splash on.

-It's perfect.

-Perfect.

-Perfect.

And it's not just about meat.

Baking bread,

roasting coffee,

frying onions and garlic.

If it smells good when you cook,

the secret chemist inside you is actually analysing

the results of a Maillard reaction...

..a reaction so complex it takes a whole textbook to describe it.

THEY CHEER

Our understanding of food

and how it seduces our senses is deepening all the time.

In the past, when eating the wrong thing could be a threat,

our senses guided us to swallow what was nourishing

and to spit out what might harm us.

'For modern humans, though,

'taste is no longer merely a guide to survival.

'Today, we transform food in ways

'our ancestors would never have recognised...

'..to create combinations that stimulate our eyes,

'noses and all our taste buds...

'..to create the ultimate mouthful of flavour.'

THEY CHEER

These days, taste is mainly about pleasure, the enjoyment in food.

And it's that enjoyment which brings communities and families together.

It's because we really understand what makes food work

that we're able to create unusual combinations,

really make our taste buds zing.

Next time, we explore why we have food on the brain.

We discover how it ignites powerful, irresistible cravings in us...

That is truly delicious!

..and sometimes disgust,

why we welcome pain

and have learnt to love the hottest food on the planet.

Can science affect your perception of food?

How instinctive are you?

To find out more about the foods you eat,

go to the BBC website on the screen

and follow the links to the Open University.