cooking with chemistry this is the first in a series of two cooking videos we're doing to
celebrate 100 complete videos we've got about 100 grams of fresh raspberries we're going to
make something tasty with them and while we do that we're going to save a few of them and see
if we can get them to react with some fun and popular reagents okay let's get cooking first
up we've got to add whites and we're going to be making the meringue with these which
we'll need for two different parts of our recipe get yourself a nice big bowl preferably metal
and make sure it's spotlessly clean especially making sure there's no trace of any oil or grease
on it you'll need an electric whisk for this and make sure it's also scrupulously
clean otherwise you won't get a good volume out of your egg whites put the two whites in the bowl
and then start whisking slowly at first in order to break down the whites and
in
incorporate air slowly
stop when they're half whisked you can still see some visible air bubbles
now we first add a heaped tablespoon of sugar to the mixture
and then a quarter of a teaspoon of cream of tartar which is by potassium hydrogen tartrate
both of these will help to stabilize our meringue
whisk until you've got a nice smooth glossy texture like this
don't allow the mixture to become too stiff however
let's do our first raspberry experiment here's about 40 mils of concentrated raspberry syrup
acid and one raspberry. There's nothing obvious happening. We'll leave this here and see how
it gets on later. First of all we're going to make a cane with sponge cake. Here's 40
grams of castor sugar and one egg yolk. Add the egg yolk to the sugar. And now we're
going to whisk it up using the electric mixer. To start with the color remains
yellow and the mixture is running.
Keep going and it becomes paler in color and thickens up as you can see.
Okay this is looking good. Now we add a teaspoon of vanilla essence to the mixture.
All mixed in.
Let's go and check to see how our raspberry is doing. Well the sulfuric acid is doing
its dehydrating job, but pretty slowly as you can see. The outside of the raspberry
is charred black, and the mixture is turning a brown color. Let's leave a little bit longer.
Continuing our sponge cake, here's 45 grams of cake flour. Use flour which has a low gluten
content as this will generate a lighter and better flavor.
We're going to add about a quarter of a teaspoon of bicarbonate of soda to this. When heated
the sodium bicarbonate will react forming carbon dioxide and give us a nice bubbly light
texture. Mix it in well.
Okay so we've got our egg yolk and sugar mixture, our meringue, and our flour which we just
prepared. We're ready to make the batter for the sponge cake now. Add some of the flour
to the top.
and sugar mixture. Now, very quickly mix this in. Don't overwork. Now add some of
the meringue and then mix this in. Then repeat the process until you've
incorporated half of the meringue and all of the flour.
You should end up with a nice fluffy batter like this. Don't forget that
you've still got half your meringue mixture. Save this because we'll need it
later on. Prepare a buttered baking tray and add a sponge cake batter mixture to
this. Spread it around and create a uniform layer. And now we're ready to
bake in the oven.
Bake for about 15 minutes at a temperature of 170 degrees C. Check every so often to
see how it's getting on and don't allow it to overcook and become too hard.
Well, our raspberry has nearly dissolved as you can see. This was a bit slow and
boring so we're going to have to find a stronger dehydrating agent in order to
do this some real justice. Here we've got another raspberry.
Raspberry, meet Phosphorus pentoxide.
Lots of it.
Well, the raspberry is pretty happy under there and there's no obvious reaction occurring.
Let's squish a hole or two in it using a metal rod.
Now it's starting to react.
We've started the raspberry dehydration chain reaction.
Pretty soon there's just a black mess remaining.
This is a lot better but it's still not spectacular.
We'll have to put our thinking caps on.
And figure out how we can really get a raspberry to react later on.
Okay, our cake is out of the oven now.
Let it cool right down.
And now we're going to use a circular template to cut our four circles of sponge.
Not perfect, but it's still going to be tasty.
Hold onto these for later when we assemble the cake.
Okay now, we're going to make a raspberry sauce.
Take a saucepan and add about 90 grams of raspberries to it.
Now add 50 grams of castor sugar.
And place on a low heat.
Stir around and crush up the raspberries with the sugar.
Pretty soon they'll start to break down and form a liquid mixture.
If the mixture starts to boil then take it off the heat and let it cool a bit with stirring.
This is looking good.
Now measure out 1.5 grams of powdered gelatin.
And add a little boiling water to this.
Then stir to make a paste.
Keep stirring until it's smooth and there are no lumps present.
Now add this to the raspberry mixture and stir in well.
Heat the mixture again so that it becomes nice and liquid.
Now we're going to filter it to remove the pits.
Use a fine mesh strainer if you can.
Keep going until you can't get any more juice out.
Then add the pits back to the saucepan again and add a little boiling water to the mixture.
Heat and stir this together and then repeat the straining process.
In this way you get all the flavor out.
You should be left with a concentrated raspberry sauce a bit like this.
Now we've got about 75 ml of whipping cream.
Remember that you're looking for a fat content high enough to whip.
Anything lower than about 30% fat won't work.
We've got our electric mixer again.
Here we go.
Nicely whipped and firm.
Before the next step, place the raspberry juice we made earlier into the fridge for 10 minutes in order to chill it.
This will help it incorporate into the cream without losing air.
Just this short time shouldn't set the gelatin.
Add the juice to the cream and stir together gently.
To form a homogenous mixture.
And now add the remainder of the meringue we created at the beginning of the video.
Here's our raspberry juice mixture.
So we've got our mousse made and we've got our sponge cake base.
We're ready to assemble our cakes.
Use the circular template to create a wrap of paper of the right diameter, held in place using paper clips.
We used a double wrap of paper which was A4 size in length for extra strength.
Now take a sheet of greaseproof baking paper and place it inside the paper wrap.
Fasten it in place using the top clip.
Make sure the paper clip so it stays in a circle around the inside of the mold.
And then create another identical one.
Place them on a flat surface such as a large plate.
Okay, it's assembly time.
Place one piece of sponge cake at the bottom of each mold.
Then add a quarter of the raspberry juice mixture.
Smooth it down and then add another piece of sponge cake on top of this.
And then finally another layer of mousse.
Leave the cakes to chill in the fridge, preferably overnight, and this will allow the gelatin to set and the cake structure will become stable.
Well, all of this cooking has fueled our creative juices and we do have one last raspberry left to experiment with.
We need to be cursed for this.
No amount of precaution is too great for what we're about to do.
In the inside beaker we've got about 50 ml of concentrated sulfuric acid.
And here's 15 ml of 30% hydrogen peroxide solution in water.
We add this slowly to the sulfuric acid in the beaker.
This seems like the wrong way round, but it's important because adding sulfuric acid to hydrogen peroxide can cause an explosion.
This is dangerous stuff.
The mixture heats up and suddenly starts to spontaneously fizz in quite a menacing way.
We've created a famed and feared piranha solution.
So let's see if piranhas like to eat raspberries.
The cakes take a little bit longer.
But not that long.
Soon there's nothing left.
Not even a trace of color.
Just a colorless solution.
The peroxide and sulfuric acid create the roxosulfuric acid in solution, which is about
as strong an oxidizing agent as you can get.
Even carbon is oxidized to carbon dioxide.
Well, a little bit of whipped cream piped on the top and the cake looks great.
The sponge is roughly the same.
The texture has the mousse so it got a nice mouthfeel and a great natural fresh taste.
Thanks for watching and we hope you'll stay tuned for more interesting reactions.