It's so obvious
that it's practically proverbial. You can't unboil an egg. Well, it turns out you can, sort of. What thermal energy
does to the eggs' molecules, mechanical energy can undo. Eggs are mostly made
of water and proteins. The proteins start off
folded up into intricate shapes, held together by weak chemical bonds. Adding heat disrupts those bonds, allowing the proteins to unfold,
uncoil, unwind and wiggle freely. This process is called denaturing. The newly liberated proteins
bump up against their neighbors and start to form
new bonds with each other, more and more as the heat increases, until finally, they're so entangled
that they gel into a solid mass, a boiled egg. That entanglement might look
permanent, but it's not. According to a chemical idea called the principle
of microscopic reversibility, anything that happens,
like egg proteins seizing up, can theoretically unhappen
if you retrace your steps. But adding more heat will tangle
the proteins further, and cooling them down
will only freeze them, so here's the trick: spin them around ridiculously fast. I'm not kidding. Here's how it works. First, scientists dissolve
boiled egg whites in water with a chemical called urea, a small molecule that acts as a lubricant,
coating the proteins' long strands and making it easier for them
to glide past each other. Then, they spin that solution
in a glass tube at a breakneck 5000 rotations per minute, making the solution
spread out into a thin film. Here's the key part. The solution nearest
the wall spins faster than the solution closer to the middle. That difference in velocity
creates sheer stresses that repeatedly stretch
and contract the proteins until eventually they snap back
into their native shapes and stay there. By the time the centrifuge stops spinning, the egg white is back
in its original unboiled state. This technique works
with all sorts of proteins. Bigger, messier proteins can be
more resistant to being pulled apart, so scientists attach
a plastic bead to one end that adds extra stress
and encourages it to fold up first. This unboiling method won't work
with a whole egg in its shell since the solution has to spread
throughout a cylindrical chamber. But the applications go way beyond
uncooking your breakfast, anyhow. Many pharmaceuticals consist of proteins
that are extremely expensive to produce, partly because they get stuck
in tangled up aggregates, just like cooked egg whites and have to be untangled and refolded
before they can do their jobs. This spinning technique has the potential to be an easier, cheaper
and quicker method than other ways to refold proteins, so it may allow new drugs to be made
available to more people faster. And there's one more thing
you need to keep in mind before trying to uncook all of your food. Boiling an egg is actually
an unusual cooking process because even though it changes the way
proteins are shaped and bound together, it doesn't actually change
their chemical identity. Most types of cooking are more like
the famous Maillard reaction, which makes chemical changes that turn sugars and proteins
into delicious caramel crunchiness and are a lot harder to undo. So you might be able to unboil your egg, but I'm sorry to say
you can't unfry it...yet.
Very cool video! Thanks for sharing! I love TED.
I thought only Chuck Norris could unboil an egg...