NANDU: In a moment, it’ll start to make a noise
The aioli
Here we call it “to break”
It’s the noise you are listening
This noise means that
We are doing a good job, the emulsion is perfect
I believe is gonna be ok
now
This noise
means we are doing great.
We almost have it.
And we have it.
We have it.
To know if it's very thick
There's a way
That is to turn the mortar
Here we have a good emulsion, see?
A perfect emulsion.
And very tasty.
DAVID WEITZ: We saw Nandu make one of the most delicious, most
impressive kinds of emulsions, aioli.
Aioli is like a garlic mayonnaise.
It's very simple ingredients.
It's garlic, salt, and olive oil.
And what he does is he mixes the salt in with the garlic,
and he crushes the garlic.
The salt pulls the water out of the garlic.
And then the water from the garlic acts as the surfactant
to stabilize the drops of the olive oil in the water.
And you saw Nandu slowly mix them together.
He crushed the garlic.
He pulled the water out.
And he slowly mixed the olive oil in, slowly emulsified it.
And ultimately, he made a solid emulsion.
The only way the emulsion can be solid is
if he emulsifies sufficient olive oil that you
get these highly compressed drops.
So they become elastic.
They become solid.
And if you watch Nandu make it, sometimes what he'll do
is he'll say, the emulsion's about to break, just as he's finishing it.
And then takes a few drops of water and adds it to the emulsion.
The reason for that is that you're so close to phase inversion.
You have so much olive oil and so little water that it can easily phase invert.
And instead of having drops of oil in the water--
you have a huge number of drops of oil in a relatively small amount of water--
and you can end up with drops of water in oil.
Then you have a very small amount of water as drops in oil.
But you don't have an emulsion.
And you don't have a solid.
Now, a simpler way of making an aioli is to add a surfactant.
Garlic is not the best surfactant.
That's why it's very difficult to make a true aioli.
To make it much more easily, what Nandu did was he
added a really wonderful surfactant.
So he took an egg yolk.
He mixed it with garlic and the water.
And that then could much more easily emulsify all of the olive oil.
Without the egg yolk, it's called allioli,
and that's the most simplest form of an emulsion.
It's also, to me, one of the most impressive forms of emulsion
because it's so little, so few ingredients,
and yet you get this solid, garlic-like mayonnaise.
Eventually, however, emulsions will fail.
So let's understand a little bit about what it means to have an emulsion fail.
In order for an emulsion to fail, you have
to lose the drops of one fluid in the second.
So you have to lose the drops of the oil in the water.
And there are several ways that this can happen.
The first thing that will happen is the fact that the oil and the water
have a different density--
typically the oil is lighter than the water--
eventually, the oil drops will come to the surface.
This will particularly be the case if the volume fraction is relatively low.
And there are several ways that this can occur.
The most obvious way is through coalescence.
Two drops come close to one another, and they
join together and form a larger drop.
Always for the failure of an emulsion, you have to lose the drops.
And so the drops have to become larger.
It's the small drops that give the emulsion its particular character.
But there is another more pervasive way that emulsions can fail
and that drops can grow.
And that is called Ostwald ripening.
And that is absolutely pervasive.
It's almost impossible to completely eliminate Ostwald ripening.
Fortunately, it's a relatively slow process,
so it's not so important oftentimes, unless you
store an emulsion for a very long time.
And Ostwald ripening is the transfer of fluid from one drop to another drop.
And remember, drops are at a higher internal pressure than the outside.
And the pressure inside-- the La Place pressure--
increases as the drops gets smaller.
So there is a driving force-- an increased
pressure-- to drive the fluid from the small drops into the large drops.