The Food Lab: Better Home Cooking Through Science

as well as to control the way the eggs come together by
moving them as they cook. For my testing, I decided to
begin with just plain eggs in order to gauge the effects of
stirring and other mechanical actions. The only additive I
used was a bit of butter in the pan to prevent them from
sticking.
A few things became clear immediately. The difference
between creamy scrambled eggs and fluffy ones has mostly
to do with the amount of air they contain at the end. As
beaten eggs are heated in a skillet, their proteins begin to
set. At the same time, the moisture within them begins to
evaporate, causing pockets of steam and air to build up
within the eggs. Vigorous stirring or shaking will cause
these pockets of steam and air to rupture, making the eggs
denser. So, for the fluffiest scrambled eggs, your goal is to
minimize the movement of the eggs in the pan, gently
folding and turning them just enough to get them to cook
evenly into large, golden, tender curds. For creamy eggs,
constant stirring is preferable, to remove excess air and get
the egg proteins to set up closely with one another, resulting
in a dense, almost custard-like scramble.
Heat had a great effect on final texture as well. When
cooked over very low heat, even gently folded eggs won’t
get too fluffy. This is because there’s not enough energy in
the pan to cause water vapor to form or to cause air bubbles
to expand vigorously. So, for fluffy scrambled eggs, you
need to use relatively high heat (though if you let the pan
get too hot, you risk overcooking—or, worse, browning—
your eggs), while for creamy eggs, cooking over low heat
gives you much more control over their texture.