Alright then, now we're going to temper the chocolate
which is a necessary process to be able to work with the chocolate
Always, whether we want to make an artistic piece, chocolates or a chocolate bar.
We always have to temper the chocolate.
Tempering the chocolate means
to force crystals to crystallize in the correct form
so that afterwards, the texture sheen and snap of the chocolate will be correct.
The traditional way, nowadays the tempering is done with machines,
but the homemade method that we still use in our workshops
the way to temper chocolate is to cool it down on a cold surface.
So this is a cold marble slab.
We cast the chocolate that is at 45-50C on the marble but we leave a small fraction in the bowl.
That small fraction will allow us later to do the second part of the tempering process.
Therefore, that chocolate, what we do is that we spread it
for it to cool down homogeneously.
Therefore when that chocolate reaches about 28C
we mix it back with the rest which is at 45C to achieve a final mixture of 30-31C.
Depending upon the type of chocolate,
not all types of chocolates need to be tempered at the same temperature.
For dark chocolate we'd be working at the temperatures I mentioned
while for milk chocolate or white chocolate we'd have to work at slightly lower temperatures.
So once we obtain this, what we do is that we mix
homogeneously
the two temperatures.
And theoretically, if I've done it right the final result should be a chocolate at 30-31C
which would be the optimal way to obtain a chocolate with the fifth crystalline form.
So the first thing we can do when we have tempered chocolate is to make a chocolate bar.
If we have a mold, we cast it inside the mold
we vibrate it
and now we would let it cool down, and after a few minutes
we'd have a chocolate that is tempered
and would have a good snap and sheen.
PROFESSOR: So you've just seen remarkable chocolate creations
from Enric Rovira And now what we want to do
is take a little bit of time and talk to you about the physics of chocolate.
Now as you will see, the discussion of the physics of chocolate
is similar to the discussion of the physics of fats
that we had a little bit earlier in this course, because chocolate, of course,
is made primarily out of cocoa butter, which is itself a fat.
You will recall that cocoa butter, that fats,
that is the fats that are in food, tend to be in the form of triglycerides.
They have molecular structures that are like this,
so they sort of have two long arms that are stuck to a third arm which
is coming off on the end.
And it's the interactions between such molecules
that actually give rise to the phase behavior of fats.
Cocoa butter, it turns out, which is the primary constituent of chocolate,
is a very special kind of fat, and it has really very special properties.
And so what we want to do right now is talk to you
a little bit about what those properties are
and to try to make it so that you love the properties as much as you
love the chocolate.
So, a good way to start out and explain to you how unusual chocolate is
as a material, is just to take a piece of chocolate
and to think about it a little bit and about the properties
that you all know and love when you eat chocolate.
And you saw this, of course, very much, when you watched Enric.
So chocolate has a couple of properties that I would like to highlight.
One is that it is, of course, a solid.
It is a solid it does not melt in your hand.
The fact that it's a solid-- you can tell, because if you break it,
it sort of snaps.
There's a snap of chocolate that occurs when you take a nice piece of chocolate
and break it.
And that's sort of a typical characteristic of a solid.
The other thing about chocolate is if you take a piece of it,
as I now will, and put it in your mouth, sorry, then it melts in your mouth
as you're eating it.
And so, if you think about it, it's really a very unusual situation.
Chocolate does not melt in your hands, but it does melt in your mouth.
You know, it's something like a 10 degree temperature difference
between your mouth and your hands, but chocolate doesn't melt in your hands
but it does melt in your mouth, and that's really
one of its essential properties.
If we go back to our discussion before of fats and their melting behavior,
then you will recall that different fats have different melting points.
And the differences in the melting points, we explained before,
by the molecular structure of the fats.
We basically pointed out that fats could be saturated or unsaturated.
That saturated fats, you will remember, pack together very well.
The molecules stick to each other very strongly,
whereas unsaturated fats were harder to pack and didn't stick as strongly,
and therefore saturated fats had higher melting
temperatures than unsaturated fats.
Now if you look at the molecular structure of chocolate--
as I said before, it's a triglyceride-- there
are sort of three different acids that make up
the three different arms of chocolate.
There's palmitic acid and stearic acid, which are on the two side arms,
and on the long arm is a oleic acid.
The side armed acids are both saturated, oleic acid is unsaturated,
and it's the packing behavior of such molecules as a function of temperature
that basically gives rise to the physics of chocolate,
which I now want to discuss.
Many fats actually have only one solid phase, but it turns out--
and I'm going to try to explain to you what I mean by this--
that cocoa butter, that is the fat that underlies chocolate,
has actually six different solid phases.
So this is the phase diagram of chocolate.
So chocolate has, as I said, six crystalline phases
that vary in temperature from 18 degrees to 36 degrees.
So the lowest phase, which people call phase one, cleverly,
has a melting temperature of about 18 degrees.
The second phase, which people call phase two, is about 22 degrees.
And then there are other phases.
There's phase four, which is 34 degrees, and phase six which is 36 degrees,
and so on and so forth.
And these are the six different phases.
And in fact, it turns out that five and six are the are the ones that--
and in particular, phase five--
is the phase that you need to hit in order
to make the chocolate that you know and love and that we saw so spectacularly
illustrated by Enric.