A Matter of Taste The Secrets of Your Food


A Matter of Taste

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

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Look at all this lovely fat and sugar. Yummy.

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Do you ever wonder why you eat what you eat,

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what cooking does to food...

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Delicious.

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..or what effect it has on your body?

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I trained as a medical doctor

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and I'm absolutely obsessed by nutrition

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and the hidden chemistry of food.

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

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each of us coming from very different perspectives.

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Truly delicious.

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Together, we have taken over

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the country's leading food science lab...

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

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It's all sunk to the bottom.

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..and to reveal some truly remarkable secrets.

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

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right down to the molecular level.

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As a botanist, I am fascinated

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by the massive diversity of edible plants on our planet.

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I'm going to put them under the microscope

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to discover exactly how their biology interacts with our own.

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So, join us, as we seek out

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the most remarkable food stories on the planet

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and reveal the hidden science of our food.

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Flavour makes our food delicious.

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

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Get that combination right and food tastes heavenly.

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But what is taste?

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Thai cuisine is particularly good

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at exciting our full range of taste receptors...

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..on one plate.

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

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There is...

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

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onion - a real sort of explosion of taste.

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

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which are going on in my mouth at the moment

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are generated by five simple tastes.

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

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'that will trigger these different tastes.

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'I have no idea which is which.'

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Salty. That's definitely salty.

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Sweet.

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

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

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This is sour.

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And this one is really hard to describe.

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This is the taste that has been most recently discovered.

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This is umami.

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The word "umami" is a derivation

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

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

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

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

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Our tongue holds around 4,000 taste buds.

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Inside them are the five taste receptors.

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In humans, this is where the taste begins

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

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dazzles each of these receptors.

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But why these five tastes?

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And why is it that some combinations taste vile

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and some taste utterly delicious?

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

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

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JAMES LAUGHS

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..and in the process,

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uncover how evolution underpins our relationship with food.

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To learn about the most unusual taste,

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I've come to an extraordinary celebration

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

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CROWD HUBBUB

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I'm here, in southern Spain,

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

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CROWD HUBBUB

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THEY CHANT IN SPANISH

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

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It's been running for over 70 years

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

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It was so much fun,

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

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As well as making a perfect food missile,

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tomatoes carry a heavy punch of umami.

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

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But what exactly is umami

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

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The answer lies inside the tomatoes.

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

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'then spin them at high speed in a centrifuge,

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

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

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and it no longer smells tomatoey at all

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because those volatile flavours have been boiled off.

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And this stuff...

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..doesn't taste tomatoey either.

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It tastes salty, earthy, meaty.

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

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It's an amino acid,

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a type of molecule derived from protein in the tomato.

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Whenever you get a glutamate molecule in food,

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it triggers that umami taste,

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fuelling a desire for more umami-rich food.

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It's our love of the glutamate in tomatoes

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

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HORN BLARES

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BELL TOLLS

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

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

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These pigs roam freely, foraging whatever they can find.

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But their favourite treats are the acorns

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that fall from the oaks every winter.

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

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Together, they make the most delicious and most expensive

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umami-packed ham in the world - Iberico ham.

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HEN CLUCKS

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It's early morning in January.

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

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for one of the most important events of her year.

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

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It is known as a "matanza",

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and it involves the gathering of an entire family.

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THEY SPEAK IN SPANISH

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PIG SQUEALS

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

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

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into enough meat to keep them going all the year.

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But butchering is only the prelude to transforming this meat

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into an incredibly powerful umami-tasting explosion.

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The secret to the intense umami taste begins

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with the extraordinarily thick layer of fat...

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

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

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the same fatty acid that's found in olives.

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

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

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

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

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The surface of the ham is under constant attack.

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

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making it yellow and rancid.

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But the meat within is protected.

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

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

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

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The meat starts to cure.

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Over the years, naturally occurring enzymes

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break the proteins in the meat down

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into their basic building blocks - amino acids.

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One of these is the all-important glutamate,

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the molecule responsible for the taste of umami.

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

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and the stronger the taste will become.

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

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By the end, these hams have 50 times

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the glutamate levels of fresh meat...

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HE PLAYS GUITAR

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

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most delicious umami-tasting hams.

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

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But there's a biological reason

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why we are drawn to the umami flavour of glutamate.

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So, the reason... Mm!

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..why this ham is so delicious

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

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And protein is essential to the building

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and running of every cell in our bodies.

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THEY SING IN SPANISH

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

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

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THEY SING IN SPANISH

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

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As food enters the mouth, it meets the tongue,

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a seething landscape of muscle, covered by spiky papillae.

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These help move each mouthful of food around.

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

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

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The glutamate enters each bud,

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where it encounters the five taste receptors.

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But the glutamate molecule has a distinctive shape

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that can only activate the umami receptor...

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

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

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We're hardwired to enjoy the taste of umami

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

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But we can't survive on protein alone.

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

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So, we have another taste receptor

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that fires off whenever it encounters the chemicals

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that give us a quick energy hit.

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Yum!

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When you bite into a strawberry,

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

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you would probably pick "sweet",

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

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'But sugar and nature seldom comes on its own.

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'It's usually balanced out by another taste -

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'the taste of acid.'

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I'm going to show you that,

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with a fantastically geeky piece of kit here.

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

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Now, I've got some distilled water here.

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OK.

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And pretty much instantly, bam.

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As I was hoping for, pH 7.

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Perfectly neutral.

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On the other end of the scale,

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

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

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

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

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

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Let's get some of that juice out.

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

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Yeah, it's going down.

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For something most people describe as sweet,

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this is pretty acidic stuff.

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Look at that. 3.5.

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Right there.

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'The pH meter is measuring

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'the number of hydrogen ions in the fruit,

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'which defines the acidity of each sample.

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'Take a watermelon.'

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Watermelon juice is relatively non-acidic.

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5.5, over there.

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'These hydrogen ions trigger our sour receptors,

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

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'is actually the taste of acid.'

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Unexpected.

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3.5 again.

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'Last up, grapefruit.'

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Huh, 3.52.

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So, this is quite odd.

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All this fruit is the same pH,

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yet people describe strawberries as tasting sweet,

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despite having a similar amount of acid.

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Strawberries have a cunning ability to hide their acidity,

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

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

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Strawberry plants have specifically evolved

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

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And that's because,

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

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

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helping the strawberries' empire grow.

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

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

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

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It's an animal deterrent.

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The mild acidic solution from the unripened fruit

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washes over the tongue, stimulating the sour receptors.

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The brain interprets this taste as unpleasant

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

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

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

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'But just at the right moment,'

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when the seeds have matured and are ready to grow,

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

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All the acid is still there,

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but the fruit becomes flooded with sugar,

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produced when hormones from the seeds announce

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they're ready to be eaten.

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The sugars react with other plant molecules

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

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

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

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So, everyone's happy.

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

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

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But the strawberry is sneaky,

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

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I love strawberries and I also love blueberries.

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

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

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

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get a few drops of juice out.

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

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

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

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

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First to be tested for sugar is the blueberry juice.

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

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

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Let's do it again with the strawberry.

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Wow, that's surprising!

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Er, that is about 8,

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

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

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So, why is it that a strawberry tastes so sweet

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but it doesn't actually contain that much sugar?

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

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HE INHALES ..is its smell.

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Surprisingly, strawberries have altered the way they taste

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using the power of smell.

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Because, alongside the molecules

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that give strawberries their characteristic aroma,

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there lurk other smells with a more crafty purpose.

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

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The aroma deceives our brain into thinking

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

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

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

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

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I still find strawberries deliciously sweet.

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It's a clever trick.

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By boosting how sweet its fruit seems to be,

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the plant needs to give away less sugar,

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while still encouraging us to spread its seeds.

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Food scientists are really interested in discovering

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just how strawberries do what they do,

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

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

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but which has far less added sugar.

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Our sense of taste is not just about attracting us

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to what's good to eat and when.

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

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Take the seeds in fruit.

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Even a few crushed cherry or plum stones can produce

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

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Rhubarb leaves contain the same chemical used to make bleach.

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And uncooked, just five raw kidney beans

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contain enough phytohaemagglutinin

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to bring on vomiting, nausea and diarrhoea.

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Here, in Peru,

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

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Eating is a dangerous business.

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The world is full of things

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that look like they could be interesting to eat.

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But some things might not be such a good idea.

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

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'The potato plant originated in South America,

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

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'because of their intensely sharp, bitter taste.'

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Potatoes belong to the deadly nightshade family,

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

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

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

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I barely punctured this with my teeth

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and already a bitter bloom is going throughout my mouth

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that makes me want to spit it out instantly.

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That's my sense of taste telling me instantly,

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

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

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Your sense of taste is really a complex chemical detector

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

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

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See all this green blush over the surface?

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

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They generally are packed in young growing tips

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to help protect the plant even more.

0:25:360:25:38

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

0:25:380:25:42

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

0:25:450:25:47

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

0:25:500:25:53

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

0:25:530:25:58

about 20 more than we have for sweet.

0:25:580:26:01

Cos sweet is nice, but bitter can be deadly.

0:26:030:26:07

Can I spit this out? Sorry.

0:26:080:26:10

So, if the original potatoes were poisonous,

0:26:130:26:16

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

0:26:160:26:20

Surprisingly, we have the Inca to thank.

0:26:220:26:25

It was in places like here,

0:26:290:26:32

in the mountains of the sacred Incan valley,

0:26:320:26:34

where the poisonous solanine was gradually bred out.

0:26:340:26:38

You know, when people talk about the Inca,

0:26:400:26:43

they tend to mention lost cities and temples and gold,

0:26:430:26:49

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

0:26:490:26:56

Everything you see here only exists to grow crops.

0:26:560:27:01

And king amongst them? The potato.

0:27:010:27:04

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

0:27:130:27:17

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

0:27:170:27:21

Martin Calisaya and his family live here in this village,

0:27:240:27:29

4,000 metres high in the Andes.

0:27:290:27:31

Their lives depend on the potato.

0:27:320:27:35

Almost nothing else will grow at this altitude,

0:27:350:27:38

so spuds provide virtually all their nutrition

0:27:380:27:41

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

0:27:410:27:45

But even with 100 different varieties,

0:27:540:27:57

a hard frost could spell disaster.

0:27:570:27:59

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

0:28:030:28:07

one that can survive even the toughest winter.

0:28:070:28:10

The only downside?

0:28:120:28:14

They're bitter, poisonous and inedible,

0:28:140:28:18

packed full of deadly solanine.

0:28:180:28:21

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

0:28:220:28:26

an ingenious technology that turns poison into dinner.

0:28:260:28:31

The trick is to freeze-dry the potatoes

0:28:360:28:38

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

0:28:380:28:42

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

0:28:440:28:48

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

0:28:480:28:53

Once a year, the Calisaya family haul their crop

0:29:030:29:07

of inedible, bitter potatoes to a site

0:29:070:29:10

that's 300 metres higher than their village,

0:29:100:29:14

ready to begin a food processing technique

0:29:140:29:17

that dates back around 2,000 years.

0:29:170:29:20

HORSE WHINNIES

0:29:280:29:30

At 4,300 metres, we reach the corral,

0:29:330:29:38

where the potatoes will be processed.

0:29:380:29:41

-BREATHLESSLY:

-Growing potatoes the traditional way

0:29:470:29:50

is incredibly labour-intensive.

0:29:500:29:53

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

0:29:530:29:56

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

0:29:560:30:01

so frost gets to them, is killing me.

0:30:010:30:04

At night, the temperature plummets.

0:30:100:30:13

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

0:30:170:30:22

This allows the poisonous solanine to leach out.

0:30:250:30:29

After a night out in sub-zero temperatures,

0:30:350:30:39

these guys are frozen solid.

0:30:390:30:42

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

0:30:450:30:49

and the treading process breaks the skins

0:30:490:30:52

enough to allow an escape route for the poison.

0:30:520:30:54

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

0:30:590:31:03

the potatoes begin to thaw.

0:31:030:31:04

With the cell walls ruptured and the skins broken,

0:31:070:31:10

water leaches out, carrying the deadly solanine with it,

0:31:100:31:14

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

0:31:140:31:19

This is it. This is the end result.

0:31:210:31:23

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

0:31:230:31:28

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

0:31:280:31:33

It is the ultimate in food security.

0:31:330:31:35

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

0:31:400:31:44

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

0:31:440:31:48

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

0:32:110:32:14

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

0:32:140:32:19

I've got to say...

0:32:190:32:20

The Quechua have learnt to outsmart

0:32:260:32:29

the incredible bitterness of poisonous potatoes,

0:32:290:32:33

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

0:32:330:32:37

Thanks to them, nearly all the bitter solanine

0:32:380:32:41

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

0:32:410:32:46

Our sense of taste, then,

0:32:580:33:00

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

0:33:000:33:03

It's actually a powerful survival mechanism.

0:33:100:33:14

Our sense of taste evolved to guide us

0:33:190:33:21

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

0:33:210:33:25

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

0:33:250:33:28

because they gave us instant energy,

0:33:280:33:30

and where things that were bitter were often bad,

0:33:300:33:32

because they might be poisonous.

0:33:320:33:34

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

0:33:340:33:38

There's another really important taste,

0:33:380:33:40

which is also often confused by the modern world.

0:33:400:33:43

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

0:33:430:33:47

It is salt.

0:33:470:33:49

We're so used to the taste of salt

0:33:530:33:55

that we sometimes forget just how weird it is.

0:33:550:33:59

Let me show you something which is really quite surprising.

0:33:590:34:02

I'm going to whizz up some coffee.

0:34:020:34:05

BLENDER WHIRRS

0:34:050:34:07

Bit of boiling water.

0:34:090:34:11

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

0:34:130:34:18

And that is really quite...bitter.

0:34:220:34:24

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

0:34:260:34:28

'to the coffee grounds.'

0:34:280:34:30

Let's give it a go.

0:34:360:34:38

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

0:34:420:34:45

The bitterness has been removed.

0:34:450:34:47

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

0:34:470:34:50

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

0:34:500:34:54

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

0:34:540:34:59

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

0:35:020:35:06

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

0:35:060:35:09

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

0:35:090:35:12

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

0:35:130:35:16

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

0:35:160:35:21

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

0:35:220:35:27

Billions of years ago, life evolved in the oceans.

0:35:440:35:48

Exactly HOW it began, no-one knows.

0:35:530:35:56

But, as the first simple cells took shape,

0:35:570:36:00

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

0:36:000:36:04

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

0:36:060:36:12

a distant echo of our ancient origins in the sea.

0:36:120:36:16

Sea water might taste terrible

0:36:180:36:20

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

0:36:200:36:26

We like it because we need it.

0:36:260:36:29

Salt is vital for life.

0:36:290:36:32

This biological need has driven us

0:36:350:36:37

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

0:36:370:36:43

transforming landscapes, like this corner of Brittany.

0:36:430:36:47

Over time, this salt marsh has been painstakingly sculpted

0:36:490:36:53

into a vast network of evaporation ponds.

0:36:530:36:57

Sophie Bonnet-Questiot is one of 250 salt farmers,

0:36:590:37:05

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

0:37:050:37:09

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

0:37:120:37:18

The technique is really the same.

0:37:180:37:20

When the tide is high,

0:37:220:37:24

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

0:37:240:37:29

It's then channelled through a patchwork of ponds,

0:37:290:37:33

each just slightly lower than the last.

0:37:330:37:36

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

0:37:380:37:40

it becomes more concentrated,

0:37:400:37:42

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

0:37:420:37:45

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

0:37:470:37:52

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

0:37:530:37:57

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

0:37:590:38:02

directly on clay.

0:38:020:38:04

The highly-prized, beautiful, crystalline flakes of salt

0:38:060:38:09

contain more moisture than common salt,

0:38:090:38:12

which means the taste lingers for much longer.

0:38:120:38:16

And being unrefined, other minerals,

0:38:190:38:21

like calcium and magnesium chloride,

0:38:210:38:24

give it a more complex flavour.

0:38:240:38:26

It's the taste of the sea.

0:38:280:38:30

And this is it. This is the end result.

0:38:370:38:41

After billions of years,

0:38:420:38:44

our bodies still rely on the same basic chemistry

0:38:440:38:48

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

0:38:480:38:51

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

0:38:590:39:03

Where there's more salt, water will go.

0:39:050:39:08

It's a process called osmosis.

0:39:100:39:13

It makes cells swell and shrink.

0:39:130:39:16

Elsewhere, the sodium in salt is crucial

0:39:170:39:20

for the functioning of our nerves.

0:39:200:39:22

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

0:39:260:39:30

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

0:39:300:39:35

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

0:39:420:39:46

..not just bitter,

0:39:490:39:52

but sweet too.

0:39:520:39:53

As well as the finest salt,

0:39:560:39:58

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

0:39:580:40:03

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

0:40:030:40:06

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

0:40:060:40:12

But when you put them together, something magical happens.

0:40:120:40:15

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

0:40:170:40:22

because, alongside our regular sweet receptors,

0:40:220:40:26

we also have some additional receptors that are only activated

0:40:260:40:29

when both sugar and salt are present.

0:40:290:40:33

So, for the maximum sweet sensation,

0:40:330:40:35

seek out the salty taste combinations

0:40:350:40:38

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

0:40:380:40:41

in the gooey liquid filling inside a thin French pancake -

0:40:410:40:46

a crepe.

0:40:460:40:48

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

0:40:500:40:53

Salt,

0:40:550:40:57

bitter,

0:40:570:40:59

sweet,

0:40:590:41:01

sour

0:41:010:41:02

and umami.

0:41:020:41:04

Together, these five tastes form

0:41:060:41:08

the foundation of our experience of food.

0:41:080:41:12

Because we put food in our mouths,

0:41:180:41:20

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

0:41:200:41:24

But, in fact, when we experience food,

0:41:240:41:26

we also see it and critically...

0:41:260:41:29

HE INHALES DEEPLY ..we smell it.

0:41:290:41:31

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

0:41:310:41:35

COWS MOO

0:41:350:41:38

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

0:41:410:41:46

And around this part of the world,

0:41:460:41:49

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

0:41:490:41:53

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

0:41:540:41:58

smelling of almost nothing.

0:41:580:42:00

COWS MOO

0:42:000:42:03

So, this is where it all begins.

0:42:030:42:06

And for someone who's used to knowing

0:42:070:42:10

cows on packets in supermarkets,

0:42:100:42:12

it's a dose of reality for me.

0:42:120:42:14

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

0:42:170:42:21

and it's allowed to curdle.

0:42:210:42:22

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

0:42:240:42:28

-You can take more cheese.

-OK, bigger scoops.

0:42:280:42:32

Yes, very good.

0:42:340:42:36

'These curds will become the finished cheese,

0:42:360:42:39

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

0:42:390:42:43

'And yet, from this beginning,

0:42:440:42:46

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

0:42:460:42:50

'..each with their own unique flavour.'

0:42:530:42:55

Oh, whoa!

0:42:570:42:59

That's intense.

0:42:590:43:01

It's like a furry animal.

0:43:010:43:03

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

0:43:050:43:10

Well, more than anything else,

0:43:100:43:12

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

0:43:120:43:16

Take a bit of cheese, cover up your nose,

0:43:180:43:21

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

0:43:210:43:24

This comte, which is normally incredible,

0:43:260:43:29

it's kind of like eating a salty candle.

0:43:290:43:32

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

0:43:320:43:35

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

0:43:350:43:39

-HE INHALES

-And it's incredible.

0:43:390:43:42

The second you uncover your nose,

0:43:420:43:44

this rush of complexity and flavour comes back.

0:43:440:43:47

It's like eating in technicolour.

0:43:470:43:49

The massive difference between the thousands of different types

0:43:490:43:53

of cheese on the planet is all about smell.

0:43:530:43:56

This simple experiment reveals the powerful effect

0:43:580:44:01

that smell can have on the flavour of food.

0:44:010:44:04

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

0:44:040:44:08

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

0:44:080:44:13

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

0:44:140:44:18

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

0:44:180:44:23

There are stories that this stuff smells so bad

0:44:230:44:26

that it was actually banned from the Paris Metro.

0:44:260:44:29

Nice(!)

0:44:290:44:31

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

0:44:320:44:37

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

0:44:390:44:44

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

0:44:460:44:50

'it needs time and it needs bacteria.

0:44:500:44:52

'Each cheese starts its journey of transformation

0:44:540:44:57

'with a specific type of bacteria.

0:44:570:44:59

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

0:45:020:45:05

'that creates their flavour and texture.

0:45:050:45:07

'With Epoisses, the rinds are regularly washed

0:45:090:45:12

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

0:45:120:45:16

'and stalks of grapes left after winemaking.'

0:45:160:45:19

-It's very fragile.

-Yeah.

-So, you take it slowly.

-OK.

0:45:190:45:23

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

0:45:230:45:27

'but, most importantly,

0:45:270:45:29

'it affects which bacteria thrive on the cheese.'

0:45:290:45:32

One kind of bacteria is called Arthrobacter arilaitensis,

0:45:390:45:44

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

0:45:440:45:48

Another is Brevibacterium linens,

0:45:520:45:55

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

0:45:550:45:59

including stinky, sulphur-based compounds

0:45:590:46:02

that give cheese its funky, sweaty aroma.

0:46:020:46:05

It's closely related cousin, Brevibacterium epidermidis,

0:46:070:46:11

can be found growing on human feet,

0:46:110:46:14

giving them THEIR funky, sweaty aroma.

0:46:140:46:18

Voila.

0:46:330:46:35

Ooh!

0:46:360:46:37

They weren't kidding about the way it smells.

0:46:400:46:43

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

0:46:450:46:48

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

0:46:480:46:52

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

0:46:520:46:56

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

0:47:000:47:06

'and get sucked up into your nose.

0:47:060:47:08

'Each smell compound stimulates a unique combination of receptors

0:47:090:47:13

'that allow us to identify the smell.

0:47:130:47:16

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

0:47:180:47:22

'and it's not particularly pleasant or appetising.

0:47:220:47:25

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

0:47:270:47:33

But...

0:47:380:47:39

..when you eat it, something magical happens.

0:47:410:47:45

The aroma compounds are released in your mouth

0:47:450:47:47

and they waft up the back of your nose

0:47:470:47:50

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

0:47:500:47:53

But weirdly, your brain perceives them as very different

0:47:530:47:56

from if you were to smell forward

0:47:560:47:58

and sniff them up the front of your nose.

0:47:580:48:00

It's called backward smelling.

0:48:030:48:05

Rather than simply smelling the pong,

0:48:070:48:09

the brain now combines the smell with the creamy taste

0:48:090:48:12

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

0:48:120:48:16

This combination of taste and smell

0:48:160:48:19

'has a dramatic effect

0:48:190:48:21

'on how we perceive a particular odour molecule.

0:48:210:48:25

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

0:48:250:48:29

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

0:48:290:48:32

This stuff...

0:48:320:48:33

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

0:48:340:48:39

It's suddenly sharp, garlicky, eggy.

0:48:390:48:44

It's just warming, comforting deliciousness.

0:48:440:48:48

This is the full flavour experience.

0:48:570:49:00

Only by combining taste and backwards smells in our brain,

0:49:020:49:06

so we unlock the food's full flavour potential.

0:49:060:49:10

Breathe normally in there.

0:49:160:49:19

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

0:49:190:49:23

'but our noses are packed

0:49:230:49:25

'with around 400 different smell detectors.

0:49:250:49:28

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

0:49:280:49:33

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

0:49:330:49:37

Whoa, that one's strong.

0:49:370:49:39

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

0:49:420:49:45

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

0:49:470:49:50

Quite aromatic.

0:49:500:49:52

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

0:49:520:49:56

'that make up this mystery meal.'

0:49:560:49:58

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

0:49:580:50:01

That's weird.

0:50:010:50:03

Almost aniseedy.

0:50:050:50:07

Smells a damp basement smell.

0:50:090:50:12

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

0:50:140:50:16

..pine cone or...

0:50:180:50:20

They're sort of spicy.

0:50:220:50:23

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

0:50:230:50:26

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

0:50:260:50:30

-Would you like to smell this one?

-OK, yeah.

-Yeah.

0:50:320:50:34

Whoa, that's strong.

0:50:360:50:37

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

0:50:370:50:41

-Is that chicken korma?

-Yes, exactly.

0:50:410:50:45

We broke down all the aroma components of this curry

0:50:450:50:51

and you smell them one after the other.

0:50:510:50:54

-And I couldn't put them all together.

-Yeah.

0:50:540:50:56

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

0:50:560:51:00

-Some strange notes, like rose, like potato.

-OK, yeah.

0:51:000:51:05

-And the pigsty.

-Maybe it was the pigsty I was smelling

0:51:050:51:08

-at the beginning.

-Sweaty.

-Yeah.

-Yeah.

0:51:080:51:10

Very, very odd, having them as distinctive things

0:51:100:51:14

and then trying to add them up to something.

0:51:140:51:16

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

0:51:160:51:18

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

0:51:180:51:21

-It just smells like it.

-Yep.

0:51:210:51:23

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

0:51:230:51:26

This experiment reveals how our noses help us enjoy food.

0:51:290:51:33

Rather than singling out individual notes...

0:51:370:51:40

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

0:51:410:51:46

instantly identifiable and delicious pong.

0:51:460:51:50

Using just 400 different smell receptors...

0:51:570:52:01

..our noses are so powerfully tuned,

0:52:020:52:04

that it's been estimated we can identify

0:52:040:52:07

a trillion different smells.

0:52:070:52:09

Like pizza,

0:52:120:52:14

roast chicken

0:52:140:52:16

or an oak-aged Bordeaux.

0:52:160:52:18

In our search for evermore delicious and satisfying things

0:52:260:52:30

to indulge our senses,

0:52:300:52:32

we've created extraordinary processes

0:52:320:52:35

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

0:52:350:52:40

But one has profoundly changed the course of civilisation.

0:52:430:52:47

It has transformed our experience and our enjoyment of food.

0:52:480:52:52

It is, of course, cooking.

0:52:520:52:54

There's evidence our remote ancestors began cooking food

0:52:580:53:02

at least 400,000 years ago.

0:53:020:53:05

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

0:53:060:53:10

one of the most complex chemical reactions on Earth.

0:53:100:53:13

Now, this is a truly wonderful piece of meat.

0:53:150:53:18

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

0:53:180:53:22

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

0:53:220:53:25

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

0:53:250:53:27

But put it on the grill over there,

0:53:270:53:29

something truly wondrous will happen.

0:53:290:53:32

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

0:53:320:53:36

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

0:53:360:53:39

-Fantastic. You don't put salt?

-No, no.

-No?

0:53:440:53:48

-No, no.

-Oil?

-No, nothing.

0:53:480:53:51

The key to unlocking the flavour in the meat

0:53:530:53:56

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

0:53:560:54:00

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

0:54:000:54:04

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

0:54:100:54:12

that is the results of the Maillard reaction.

0:54:120:54:15

It starts off simply enough.

0:54:180:54:20

In the intense heat, the building blocks of protein,

0:54:200:54:23

the amino acids,

0:54:230:54:25

react with naturally occurring sugars in the meat.

0:54:250:54:28

And the beauty of the Maillard reaction is that,

0:54:280:54:31

once it kicks off, everything goes completely crazy.

0:54:310:54:34

The reaction becomes more and more complex

0:54:390:54:42

and intensifies as the products of each reaction

0:54:420:54:46

get involved in their own reactions.

0:54:460:54:48

Eventually, the whole thing cascades wildly

0:54:500:54:53

and generates thousands of different molecules.

0:54:530:54:56

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

0:55:030:55:06

HE INHALES ..hungrily hovering up.

0:55:060:55:09

Smells absolutely fantastic now, I have to say.

0:55:140:55:17

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

0:55:170:55:19

-to what it is now.

-Ora, sale grosso.

0:55:190:55:23

-Oil.

-OK. Olive oil, splash on.

0:55:260:55:28

-It's perfect.

-Perfect.

-Perfect.

0:55:340:55:36

And it's not just about meat.

0:55:430:55:45

Baking bread,

0:55:470:55:49

roasting coffee,

0:55:490:55:51

frying onions and garlic.

0:55:510:55:54

If it smells good when you cook,

0:55:570:56:00

the secret chemist inside you is actually analysing

0:56:000:56:03

the results of a Maillard reaction...

0:56:030:56:06

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

0:56:100:56:15

THEY CHEER

0:56:150:56:17

Our understanding of food

0:56:240:56:26

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

0:56:260:56:31

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

0:56:330:56:36

our senses guided us to swallow what was nourishing

0:56:360:56:40

and to spit out what might harm us.

0:56:400:56:43

'For modern humans, though,

0:56:450:56:46

'taste is no longer merely a guide to survival.

0:56:460:56:50

'Today, we transform food in ways

0:56:530:56:55

'our ancestors would never have recognised...

0:56:550:56:59

'..to create combinations that stimulate our eyes,

0:57:000:57:03

'noses and all our taste buds...

0:57:030:57:06

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

0:57:070:57:11

THEY CHEER

0:57:110:57:13

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

0:57:130:57:18

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

0:57:180:57:22

It's because we really understand what makes food work

0:57:220:57:26

that we're able to create unusual combinations,

0:57:260:57:29

really make our taste buds zing.

0:57:290:57:31

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

0:57:330:57:37

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

0:57:380:57:43

That is truly delicious!

0:57:430:57:45

..and sometimes disgust,

0:57:450:57:47

why we welcome pain

0:57:470:57:50

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

0:57:500:57:54

Can science affect your perception of food?

0:57:570:58:00

How instinctive are you?

0:58:000:58:02

To find out more about the foods you eat,

0:58:020:58:04

go to the BBC website on the screen

0:58:040:58:07

and follow the links to the Open University.

0:58:070:58:10

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