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