So let's start with caramelization.
On a famous desert, Crema Catalana.
Here we have the cream already made and cooled down
with that think skin that forms on the top and that will help us to add the sugar
to make that crystal that we want to make
all at once ... we need to be generous.
but it is important to spread it evenly
in order to be able to apply the iron.
The iron needs to be red hot
at a very high temperature.
So we apply the iron on top of the cream
To achieve that burnt aspect, giving it that effect.
Obviously right now it'd still be soft
but it hardens instantaneously.
If you want we could show how it breaks.
What do you think?
Here's that instantaneous caramelization effect,
to yield that sound ...
Aah ... it cracks.
That crystal, that sugar crystal.
Now go ahead and taste it.
OK, thank you.
Mmmm ... I love Crema Catalana. Thank you.
Thank you.
So caramelization is just what happens when you heat sugar,
white table sugar.
So sugar is just a sucrose molecule
and sucrose is made of fructose and glucose.
And so the first thing that happens when we apply heat
is that these two molecules fall apart
into glucose and fructose.
And so here is what these ring structures would look like.
And then these ring structures just sort of explode
into a wide array of other small molecules.
And all of these molecules have different flavors
and different smells.
And typically in caramelization,
the flavors that we're talking about
are these sort of sherry, buttery, nutty flavors.
And this happens at temperatures of about 165 degrees Celsius or higher.
So if we were to take these flavors
and put them on what we call a flavor wheel,
which is what wine tasters
or tasters in general would use
when they would try to sort of guide their
pinpointing of what a flavor is,
and here's a flavor wheel with all of the different flavors
everything from earthy to nutty to fruity to flowery
And so caramelization kind of creates
these particular flavors
that are sort of caramely and nutty-buttery.
And so now keep this in mind
because now we're going to move on to Maillard reactions
and see what kinds of flavors those create.
Maillard reactions, in contrast to caramelization reactions
involve the reactions between sugars and amino acids.
And these typically take place at temperatures above 120 degrees Celsius.
And so what happens here is that
if you for example just take milk
and heat it
There's going to be sugars in the milk and there's going to be
proteins in the milk
amino acids
And the sugars are going to react with the amino acids
And create these sort of browner compounds
that have nutty flavors
And so you've probably had this
If you've ever had dulce de leche
you've had this exact same thing
and there are a lot of desserts and a lot of sauces that build on this concept
of just heating milk
and creating these flavors.
And so there are many different kinds of amino acids
There's about 20 amino acids
And each of them, the first step
would be that the glucose
reacts with the amino group
on any of the amino acids
And so the amino group, it is a nucleophile
if you think back to chemistry
And the nucleophile is going to attack the carbon
on the glucose, here.
And this is then going to form a bond
And this is kind of the first step
in the Maillard reactions.
And after this there is a whole
again, just an array of different reactions
that can happen
The molecule falls apart
it reacts again
it reacts with each other,
with other glucoses, with other amino acids
but this is the first step.
And so you can imagine then, that if there is
20 amino acids, and this is the first step
you can imagine that there is just a lot of different molecules that can be created
Even with this just being the first step.
The characteristic feature of Maillard products
is that they often contain sulfur and nitrogen
which come from the amino acids in the protein.
And sulfur in protein often contributes these kind of meaty
earthy flavors that we associate with when we cook a steak
and there's this sort of earthy, meaty flavor
and this also then contributes to a lot of the other sort of non-distinct flavors
that are very different from the flavors that we get in caramelization.
Another feature that makes Maillard reactions special
and interesting from a chemical perspective
is that they're often exothermic reactions.
Exothermic reactions produce heat as they happen.
And so as Maillard reactions start to happen
they produce heat, and then this leads to more reactions happening.
And so this speeds up.
And so you may have experienced this, actually, if you have ever made toast.
So sometimes you may have experienced that you make toast
and you wait, and wait, and it's not done, and it's not done,
and then suddenly it's done and then it's done and then it's overdone
and they just happen very, very quickly.
Millard reactions, of course, are not only in baking
but they are basically everywhere around us.
Here are just some examples.
Everything from coffee to popcorn to champagne
to a nice cured ham are all places where Maillard reactions have taken place
And in some of these cases there hasn't even been an addition of heat
So in champagne, for example
the reaction is allowed to take place over so long
that the reactions take place anyway, even though there is no input of heat.
But all of these sort of earthy flavors that you get
in a champagne, or in meat
they're all also due to Maillard reactions.