Right, guys, taste this yeast extract.
Try some of these.
Oh, you don't want it! HE LAUGHS
Mmm! I like it too!
Eugh! Horrible.
There are some foods that completely divide us.
Unbelievably yummy for some, and downright yucky for others.
How do the food factories come up with tastes that give us such extreme reactions?
So what does chocolate mean to you?
Everything. It's a necessity.
Couldn't live without it! We are chocaholics.
Would you chew this?
No. Have a go!
What do you reckon this has to do with a piece of chewing gum like that?
I'll be revealing the secrets behind some of the foods that delight and disgust us by making them,
food-factory style.
There are some foods we buy week after week, while others never make it on the shopping list.
So what makes us love some foods and loathe others?
And what goes on behind the scenes to create these monsters or marvels of the supermarket shelves?
I'm going to set up my own food factory in this barn to find out how it's done.
It may look as though it's full of junk, but it's got everything I need
to discover the secrets of supermarket food.
Now there is one supermarket product that really divides people
on the yuck-yum spectrum and it's this stuff, yeast extract.
For some people, it has a taste to die for,
for others, it tastes like something's died.
Got a little something for you.
Tell me what you think of it and then tell me what the flavours are?
You don't like that at all? No. You're not a big fan.
That's mustard.
Yeasty. Yeasty.
Sort of musky in a good way. Beefy salt.
I could easily have that on toast. You'd enjoy that? Oh, yeah.
So what gives it its massive flavour?
Here in the barn, I'm fully equipped to go back to basics and make my own yeast extract.
Clearly, the main ingredient
in yeast extract is yeast.
This stuff. You'll be familiar with yeast if you bake bread,
it's what makes it rise.
But did you know it's a fungus?
We can also thank it for the alcohol in our beer and wine.
But being one of the yeasty boys isn't easy.
MUSIC: "Funeral March" by Frederic Chopin
When you turn yeast into yeast extract, something terrible happens.
Now it sounds dramatic, but all the yeast must die.
In fact, the individual cells that make up the yeast
have to self-destruct then splurge out their innards.
It's like the yeastern front out there.
To extract the extract, scientists use an instrument of torture called a bioreactor.
I could do with a cup of tea.
I couldn't find a bioreactor in the barn so I'm using a tea urn instead.
In here will go the yeast cells and some water.
To keep everything moving, I'm using the motor from an ice-cream maker.
CHILD'S MOBILE JINGLE PLAYS
That's going to be my stirrer.
Like a bioreactor, this should mix together the cells and convince them to give up the ghost.
# No more Mr Nice Guy... #
Right, this is how it's going to work.
I've filled my urn up with water and it's got a nice heating element inside it
which is going to keep the water nice and warm, around 50 degrees Celsius.
Inside, I'm going to put my yeast.
Now this is dried baker's yeast but the yeast-extract factories
use the waste yeast from the brewing industry.
Now, in that goes. Right, let's give that a stir.
Now it's time for my last ingredient, which is pretty deadly,
it's going to cause these yeast cells to self-destruct and then splurge their insides out.
And the killer ingredient...
..salt.
It starts a natural self-destruction process in the yeast.
But I want to look at this more closely.
Now under the microscope, yeast looks like this.
Now each one of those blobs is a living cell
that contains, amongst other things, a surprising amount of water.
The salt draws water out of the yeast cells and they start to die.
This triggers the production of chemicals
that weaken the cell walls and wreak havoc inside their insides
Now once the walls of the cells are damaged, everything starts to ooze out.
It sounds yucky, but this yeasty ooze gives the extract its yummy taste.
Right, time to turn it on.
It'll take a few hours to work, but with luck, by tomorrow, all my yeast will have died off.
Well, I'll leave these guys to their fate, they're doomed.
MUSIC: "Funeral March" by Frederic Chopin
I love the smell of onions frying.
It's already got my mouth watering.
But I hate chopping them. It's a bit embarrassing really -
a vegetable making you cry?
How do you stop yourself crying when you're chopping onions? Keep the end on.
I've heard that if you suck a small spoon...
Contact lenses. With your lenses in, you don't get any watering? Yes.
'Another way to chop without weeping is to wear onion specs.'
Try those on. All right.
'They fit tightly around the eyes and stop any onion vapour from getting in. Very fetching.'
Are they making your eyes water? No. No.
No. There you are, they work. Brilliant job. Yeah!
'Whatever we do to try and stop the tears...'
Woo!
'..we'd all prefer onions didn't make us cry.'
One person who literally knows her onions is Dr Gemma Chope from Cranfield University.
And where better to meet her than in the middle of an onion field?
Why do onions make us cry?
Well, this onion here is a really rich source of sugars,
so it's really attractive to predators and pests,
and over the years,
it's developed quite a few chemical weapons to defend itself.
So it's got its own chemical weapons,
it hasn't just got a grudge against us, then?
No, it's nothing personal against humans, no!
Right, OK. Let's go!
'The crying chemical is really a defence mechanism against predators.
'Onions aren't alone in using natural defences to protect themselves.
'Nettles do the same thing when they sting you.
'And Gemma's brought along the daddy of all natural defences.'
Yep, Just going to waft that around... That st... HE COUGHS
That stinks! I bet nobody invites you to parties! That is wrong!
Man alive!
What's wrong with you?
Who's made that smell?
Well, actually, I can show you.
That's an animal I recognise immediately.
Absolutely, this is a skunk. Lovely, isn't he?
What on Earth has an onion got to do with this lovely creature?
The link is based in sulphur.
Sulphur is at the basis of the skunk's defence system and it's the same with onions.
You'll find sulphur in gunpowder and insecticides.
Mr Skunk uses its whiffy smell to chase away predators,
while onions employ sulphur to blind us with tears.
I have to say, it's not having much effect on Gemma's little friend.
But exactly how does sulphur in onions reduce us to floods?
Even when you start peeling the skin, you get that hit of onion, don't you?
Every time you chop with a knife, you're breaking up the cells in the onion.
You're allowing two different types of sulphur-based chemicals to mix.
And it finishes up in a molecule that's so light it, flies up from the onion and gets you right in the eye.
Yeah, you do get it. SHE LAUGHS
Straightaway. But I always think that...
SHE LAUGHS
# You upsets me, baby
# Yes, you upsets me, baby... #
This sulphur-based molecule irritates the nerve endings in our eyes,
which switch on the waterworks as we try to wash it away.
And the stronger an onion tastes, the more sulphur it contains.
But now there's a new onion in the supermarket.
Farmer Paul Cripsey has spent ten years developing a milder-tasting onion that won't make us cry.
Could he have turned a yuck into a yum?
Right, so the big test is, will it make me cry if I chop it?
No, it won't Jimmy, it won't.
Oh, the smell comes across straightaway.
Look at my eyes, into my eyes, not round my eyes. But no tears.
No tears. So how do you achieve that? The sulphur creates the strength,
so we must limit how much sulphur. Half of it's really in the breeding of the onion.
But also we have to have soils which are low in sulphur,
and when we feed it, we must put no sulphur into the soil.
Because if you put too much sulphur in, the onion will be strong. Bit of a balancing game.
But if sulphur gives an onion its strong flavour, will a sulphur-less onion be bland and tasteless?
Have a bite of it now, see what it tastes like. Are you sure? Eat it like an apple, try it!
That's really sweet. Has this got more sugar in it than a normal onion?
All onions have the same amount of sugar, but this one's
got less sulphur, so it's not masking the sweetness. Let's have another go.
Mmm! Enjoy it? Yeah.
My wife's going to go mad with all this onion breath!
If you like your onions mild and sweet,
there's no need for tears in the kitchen any more -
the no-cry onion is here.
But if you like your onions with a bit more flavour,
then you'll have to hang on to your goggles a little bit longer.
Back at the barn, I'm making something you either love or loathe. Yeast extract.
I've been heating yeast in this tea urn all night
to make the yeast cells burst open so I can get at their yeasty delights.
But it's not gone according to plan.
Look at this, this is a bit of a disaster site, now last night,
the thermostat on the tea urn went and the whole thing has boiled over, I've even sprung a leak.
It's like my yeasts are trying to resist self-destructing.
But they're not going to escape that easily.
I've managed to save some and I'm heating it in the oven.
Now it smells totally different.
Before, it was fairly fragrant, it had a bready-type smell about it.
Now the smell's much heavier. Let's have a look at the colour.
Well, all the lumps have dissolved and it's turned beige
and it's quite gloopy as well.
In here, should be the insides of billions of yeast cells.
Now these small fragments have a very strong flavour and that's what I'm beginning to smell.
The same thing happens when you cook meat. The protein breaks down
into small fragments that have a strong flavour.
That's why yeast extracts can taste meaty, even though they're vegetarian.
But this stuff is way too watery to spread on my toast.
I need to get rid of some of the liquid.
To do that, I need to build something called an evaporator.
Luckily, everything I need is in this barn.
I knew that sheet of corrugated metal would come in handy
It's amazing what you can knock together with a bucket and some pipes.
Right, that's all in. Now, this is my evaporator,
and how it works is, my yeast extraction is going to pass
all the way through this pipe here
and come out here on these four little copper pipes, run along this
corrugated metal sheet and I'm going to be blowing lots of heat
through it with this space heater to heat it up so, hopefully, it will begin to evaporate and at the end,
I shall collect some nice, thick, concentrated yeast extract that, hopefully, I can spread on my toast.
Look at this, here it comes!
Got to get the flow just right, if it's too fast it will just run
all the way to the end. If it's too slow, it could begin to dry.
It's like a yeast race.
These rivers of yeast extract allow me to drive off lots of water,
leaving behind a concentrated goo.
Now I've got the flow just right, it's just dripping out
and slowly travelling down the little channels
and it's getting hotter and hotter so the water's evaporating,
so as we get right to the end - look at that bubbling away -
so that yeast extract
is getting nice and thick now, so I might start collecting that.
# Drip, drip
# Drippity-drop... #
Look at that, it's becoming really pasty.
Not quite enough for breakfast yet,
but that's not bad.
My effort is a lot lighter than the dark-brown stuff you get in the supermarket.
I think it could do with being more concentrated, but we're on our yeasty way.
# You know this empty room is driving me insane... #
That is the same consistency as the yeast extract
you would get in the shops. That would spread beautifully.
Mmmm. I can't resist the smell any longer.
Time for the toast test.
That's not too runny,
not too thick,
that's just right.
Let's have a little taste.
It's very yeasty.
HE LAUGHS
That is borderline on the yuck,
it's a bit like beer that's gone off
and it's not as salty as the stuff you buy in the supermarket
but it's not right.
You wouldn't have that for breakfast and go out and have a good day.
There we go, my very own yeast extract.
# Yummy, yummy, yummy I got love in my tummy... #
Later, we made some more to the same recipe, only this time we cooked it longer, so it looks browner.
So, yuck or yum?
I am an expert. I have it every day.
I love it. It's edible.
So is cardboard! Yeah!
Tastes similar but not the same.
You really hate it. Mmm.
It tastes like horrible cheese. I'll take it way from you,
cos it's making you pull some interesting faces!
Yeast extract is one of those foods that gets extreme reactions.
By there is one food that seems to please just about everyone
and that is chocolate.
But giving chocolate its glossy irresistible appearance
is not as easy as you may think.
# Candy man
# Hey, candy man... #
For almost 75 years, this factory in Halifax has been churning out chocs.
For not nearly as long, Marie Guest has been making sure around seven million
of these little beauties roll off the production line every day.
# The candy man... #
Marie, tell me, what do the British public want from their chocolate bar?
They want really good, shiny chocolate with a really good snap.
So isn't chocolate naturally shiny?
No, it would be dull if we didn't process it correctly.
Can I lick my fingers? No, Jimmy, not in a food factory.
It's hard working here, you can't lick your fingers when you've got chocolate on it!
I wouldn't last a day!
# Golden brown
# Texture like sun... #
To give chocolate a sleek and shiny coat it has to be kept at the right temperature.
That's the job of chocolate wizard Marie Wainwright.
My job is to get it from this liquid form into this solid form
and still shiny, but not like this, which is dull.
Right, you can see the difference there.
If I snap that, look at that. It hasn't got a snap to it has it?
It hasn't got a snap, no. It's very crumbly.
Very crumbly, that whirl to it.
Give this one... SNAP!
Oh, now you're talking. Look at the difference!
So how do you get your chocolate nice and shiny?
When I start to cool the chocolate, I get all fat crystals forming
and what I want is these crystals all in a uniform shape.
So what happens if the chocolate cools a bit willy-nilly?
What happens then is you get all sorts of different crystals forming
which are all different shapes and they won't pack tightly together.
Right, so you get all these odd crystals forming.
The light coming in would just scatter off and you won't get the shine.
That's right. So the even crystals,
all neat and tidy, the light comes in, bounces off and it's shiny like a mirror.
That's right.
To make sure the chocolate crystals are the proper shape, it goes through a process called tempering.
And the secret of tempering is temperature control.
If they're too hot or too cold, the chocolate crystals
will be the wrong shape and we won't get shiny chocolate.
Wow. This is one of the temperers that we use to temper our chocolate within the factory.
So this is the heart of the chocolate factory? It is, absolutely, yes.
The temperature of the chocolate in here has to be kept within strict limits all the time.
# Lick your lips, blow me a kiss
# Take a nibble of chocolate bliss... #
So worst-case scenario, say if something goes wrong, what happens then?
If it's got a centre in there, for instance,
caramel and hazelnut, we can't recover that, so that is waste.
Right, I've just found a little opening for me.
I could eat all the wasted ones.
I'll bring my own chair and everything.
Are these peppermints? These are actually orange creams, soft centres.
This is before they're actually enrobed in chocolate. There was a bit of controversy in my house.
When I was growing up, you either loved them or hated them
and I liked the green triangles and my mum loved these,
but if she was to bite into one of these her teeth would come out!
We need a hard structure so that we can actually coat it in chocolate.
How do they go soft then?
The sugars start to break down, there's a chemical reaction, so they become softer over,
I would say about three days, but they don't go completely soft.
But how do you know that chocolate is going to be shiny?
Well, we don't, we only know that when we actually take the product out of the moulds.
So you've got to wait until they go through the whole process to see if they've got a shine? Yes.
Doesn't that worry you? I'd be petrified.
With the chocolates out of their moulds, there's only one thing left to do.
This is my number-one yum.
Here they are off the production line, all looking lovely, but are they shiny?
Check them, Jimmy, have a look at them.
Right, it's your reputation at stake...
Yep, nice and shiny.
What about texture? Has it got the snap? Try it! You tell me.
Mmm! Lovely snap.
Need to test it again, obviously.
Is there a job going here where you need quality control?
Would you like to be our quality control check, yeah?
I've got a good CV. At the top it says "greedy"!
Mmm! I feel a bit sick now!
Next up on my yuck-yum top four is something to get your teeth into.
Chewing gum.
Chewing gum is a unique product.
But is it even food?
And if it is, why doesn't it disappear when you chew it?
Well, to find out, I'm going to make my own.
Here in the barn, I've got everything I need to unstick the secrets of chewing gum.
And it all starts with something called gum base. But what on Earth is it?
Gum base is actually a mixture of ingredients.
It's strange that chewing gum companies
don't have to put them on the label, because there's quite a few of them.
But usually they're a trade secret.
So what are the secret ingredients of gum base in chewing gum? Well, I can tell you...
you won't find many of them in your local supermarket. Look at this.
It's sort of like a liquid but it's not, it's a solid as well.
'Its called polyisobutylene,
'a type of rubber...'
Look at it! HE GROANS
'..used to make basketballs and the inner lining of car tyres. Delicious!'
Now you can eat all of these ingredients,
they are food grade. Look! Ooop!
# I'm gonna chew Won't give it to you... #
It's like chewing an elastic band.
Next up, these little guys. Polyvinyl acetate.
This is a plastic that goes rubbery when it gets warm.
Let's have a little taste of one or two of these.
You can use these to make glue. I hope they don't stick my teeth together.
Hmmm. Really unpleasant.
Then we've got big slabs of wax, this is very similar to the stuff you make candles out of.
Then there's rosin, which is made from the sap of pine trees.
And then something we're all very familiar with...
talcum powder.
So how do you turn all these weird ingredients into lovely gum?
My first job is to make the gum base.
So I've got to heat all these ingredients and mix them up.
But before I do that, I've got to kit up.
Hot, molten rubbery stuff is not something you want
to get on your skin because it burns like crazy and it sticks as well, so it wouldn't be much fun.
First up, it's polyisobutylene.
HE LAUGHS
There's the first bit. HE LAUGHS
Little bit of talc, which is something I thought I'd never say.
Oh, yeah, it makes it look much better.
Time for a bit of polyvinyl acetate, which I find is always essential at this point.
Does that look like chewing gum to you?
HE LAUGHS
Polyisobutylene and polyvinyl acetate stretch when they're heated.
And without them, chum...no gum.
It's like the Creature From The Black Lagoon.
# Beware of The Blob It creeps and leaps... #
You can never over-season your chewing gum with too much talcum powder.
There's an incredible change going on.
It's really starting to come together and look like runny chewing gum.
Next goes the pine-tree extract.
That's the kind of thing I used to have stuck under my desk at school.
Big lump of chewing gum. It's probably still there.
Right, time for everyone's favourite, little bit of wax.
The wax, rosin and talc change the chewiness of the stretchy rubbers.
The gum needs to be solid at room temperature but soft when heated in the mouth.
# Be careful of The Blob... #
Right, I think that's as good as it's going to get.
Look at that, lovely stuff.
But not very tasty.
To fill my rubbery blob with flavour, I need to build a very powerful mixer.
I'll mix my gum in this steel container.
The mixing blade is turned by a length of motorcycle chain.
And the power comes from this monster motor.
Builders use it to mix thick cement.
Finally, I need heat. These wallpaper steamers should do the job.
They attach to holes at the front of the mixer.
Right, let's put it all together, and see if it works.
I've got my wallpaper steamers connected up to this mixer
because I want to keep it nice and hot because if I don't, the gum base will go solid.
It seems to be working.
Time to mix some sweetness into my rubbery gloop...
with glucose syrup.
Right, that's enough of that. Next ingredient, bit more sugar.
In fact, quite a lot of sugar.
Mint flavouring.
That smells incredible.
But as we all know, the flavour doesn't last.
That's because when you chew, the sugar and flavour dissolve, leaving behind a hard ball of gum base.
because gum base is a type of rubber,
it won't dissolve in your mouth no matter how much you chew it.
Time to get out my mixture. It's just about ready.
To make this gum look like the real deal, I need to get mangling.
Look at that, probably a year's worth of chewing gum here.
Well, there will be, if I can get 125 pieces out of this one sheet.
In the UK, that's how much your average gum fan consumes in a year.
You see, I forget, I keep thinking I'm cutting something
like pasta dough, but in fact, it's a rubber concoction
that gets really hard when it gets cold.
So it's like cutting through a bicycle tyre.
Hope it doesn't taste like one!
Look at that, it sort of looks like chewing gum,
it smells like chewing gum, funny little colour, but do you know what?
After putting all those ingredients in, I'm not sure about putting this in my mouth,
because it seems like a load of plastic and wax went into it. But let's have a go.
Oh, I don't know.
Ugh.
It does taste like chewing gum,
but it's like eating dried cement.
Oh!
You carry on chewing, and it begins to form...
chewing gum.
But the initial stages are repulsive.
HE CLEARS HIS THROAT
Look at that. It's like a little...
Well, it's like chewing gum.
It's a lot harder, almost like a bit of clay, but for a product tha
seems impossible to make in your home, we've just about done it.
# I put the penny in the gum slot... #
They're so thick I can only get three in the box...
There we go, my very own mint chewing gum.
# I put the penny in the gum slot Eenie, meenie... #
But will I come unstuck when they get chewing down on my farm?
This is my version of chewing gum. Thank you.
It's not easy to chew is it? It's like eating Plasticine.
I can't actually chew mine at the moment, it's still almost solid.
That's awful. I don't mind it.
Out of ten, what would you give my chewing gum?
Seven. Seven? That's quite good.
Seven. Seven!
What would you give it? Erm, two.
I can feel my fillings coming out now.
I probably go six. Sorry!
You're saying six, you're thinking two.
They're too kind.
Whether you're crazy about these foods or they drive you crazy,
food manufacturers try hard to make us love their products.
But when it comes to the crunch,
it'll be your taste buds that decide.
Subtitles by Red Bee Media Ltd
E-mail subtitling@bbc.co.uk