Hi, I'm Jennifer
Castella Cake is one my favorite desert
We can start with pricniples I went through in "How to Rise Dough" - Doug 101 Episode 4
In my last episode, I used this technique to make Chinese Steamed FlourCake
But that method has too much gluten
It is fluffy but not soft enough for cake
Using yeast to leaven dough doesn't work for cake
A chemical leavening agent like baking power can work
Eggs can also be used as a phyiscal leavening agent
When they are whipped up, they will trap air bubbles
Allowing dough to rise as well
It will also add flavor to the dough
#1 Start with fresh eggs
The fresher they are, the more air it will trap
#2 how you whip will determine how much air it traps
#3 adding other ingredients helps to stabilize the bubbles
Let's start with splitting the egg white & egg yolk
Iwill whip them separately
to show you their different characteristics
Once you see the difference
You can play with different combinations
to get the texture & flavor you need
by using different ratios
1st experiment, whipping at difference temperatures
Did you notice the colder egg white whipped faster and hold their shape better?
Summary is, egg white is better whipped cold
Chefs often put vinegar in the egg white before beating
To find out why, I'm going to do a 2nd experiment by add vinegar to 1 bowl to see the difference
The one with vinegar whips noticeably faster
But the one with out vinegar
turned out better
Now let's try lemon juice instead
The result is the same
The one without vinegar turned out better
So why then do chefs put vinegar or cream of tartar in the egg white?
Let's set the egg white aside for a bit and see
After 30 minutes, you notice the one without vinegar
leaked a lot of liquid
The one with vinegar had less and held it's shape better
So the main reason you'd add something acidic
is to help the whipped egg retain it's shape longer
3rd experiment: Let's see 2 different ways to add sugar
1st is to add it all at once and 2nd is to add in small batches
It turns out adding in batches whips faster
Let's set it aside to see how stable they are
30 min later, no noticeable difference
How you add the sugar main affect how fast it whips
Now let's try salt and no salt (common ingredient)
Let's see if there is a difference in stability
Very little difference
Let's summarize the 3 experiment results
#1 Adding sugar in batches will whip faster
#2 Adding vinegar helps stabilize the whipped egg
#3 Use refrigerated egg white to whip faster
Often instruction will stress you can't have egg yolk
Let's do an experiment and have 1 bowl with some egg yolk
and another with a bit of egg yolk
Seems the bit of egg yolk didn't really affect it
So you don't need to be so precise
The one with more yolk can't be whipped to full volume
but it can still be useful for making different type of cake
we will talk about that later
Many instruction also talk about having a very clean bowl (no oil or water)
Here I'm going to delibrately add some oil or a bit of water
to see what it does
Seems like not much of a problem if you
have a little bit of water or oil
You can use a hand mixer or a table top mixer
doesn't really matter
The slow to fast is because of the nature of egg white
Egg white contains 12% protein
proteins are made up of long chains of amino acids
One side of the chain likes water
The other dislikes water
It's this characteric that forms the foam
Starting slow will help the chains to loosen
at this point
you should see the clear egg white turn opaque
and soapy
Now you can increase speed
and start adding sugar in batches
Other than the protein, egg white has 88% water
The hyrophallic group of the chainwill seek out water
and the hydrophobic group will seek out air
This reconfiguration creates the foamy texture
I didn't add vinegar this tim
mainly to demonstrate slow to fast
But if you want to stabilize the foam, you should add vinegar before starting
Adding sugar during whipping also help to stabilize
It will make the foam texture stickier
But adding it too early (before it become foamy)
will make it harder to whip
Now let's try whipping the egg yolk
Egg yolk is mainly lecithin plus small amount of water
1 end of lecithin like water (hydrophilic)
and the other end is attracted to fat (lipophilic)
But just beating it doesn't form a foamy texture :(
The reason is because lecitin is tougher
You need to heat it up for it to whip properly
Also, there isn't enough water
Here I'm using steam to heat up the yolk
Heating and whipping should happen at the same time
If the yolk is heating too fast, you can put it aside for a bit
Few minutes later, the yolk turns foamy
The volume is not as big as egg white
But it still ballooned up about 3x
Let's see what else we can do to improve
French Sabayon style adds sguar to the mix
Adding sugar doesn't seem to make a difference at first
But let's set it aside for a white
The batch without sugar became liquidy
The batch with sugar held it's form and looks silkier
To summary, egg yolk can be whipped into foam
You will need to heat it to about 50C for best effect
Adding sugar will help it retain it's shape and makes it silkier
Egg white has bigger volume and will make fluffier dough
But egg yolk has fat and makes dough silkier, more moist, and tastier
In the next episode, I'll show you how to make cake with whipped eggs