Yum
Yum, Yum, Yummity, Yum.
But they are more than that (there is more than “Yum”? Surely not. But there is).
Oh so much more.
There is the SCIENCE of yum.
OK its normally called Food Science.
But "Yum-Sci" is realy wHat it means,
And there is loads of great Yum-sci and it has created a wHole new cuisine - molecular gastronomy)
I could talk about wHy bread becomes toast.
WHy you rest a steak (no it's not tired)
WHy squid should either be just cooked or cooked for ages.
WHy a baked alaska can even exist.
But in my cookery book, few things beat the science of wHipped up egg wHite.
If you wHip egg wHites they form a foam- loads of tiny bubbles of air surounded by said water and protein.
Add a spot of yolk, or oil and try with almost all your might, that foam just ain't gonna happen.
Alternatively if you want to wHip up a meringuey delight at speed. Do it in a copper bowl. Or with warm eggs. Or a pinch of tartaric acid or yes some sugary sweetness. And wHite, peaky peaks of floaty, eggy yumness will soon sit before you.
So wHat's the story?
Egg wHite proteins (egg albumins) are globular. Tangled chains of amino acids wrapped around themselves into vaguely blobby shapes. Some amino acids love the water they are surrounded by and hang out on the outside (hydrophilic is the Yumaciously technical term) and others are water loathers, water avoiders, water haters (hydrophobic to all you scientist dudes) and all these hang out in the centre of the tangle ball, safe and secure from the wide wet world..
Then you start to beat, wHisk and wHip.
This creates shear forces on the albumins, pulling at them, stretching them. CHANGING THEIR SHAPE. Yes DENATURING them!. But unlike cooking, not permanently so. Leave your wHipped wHite for a wHile and it will turn back to its old see-through, slimey self.
BUT stretched egg wHite proteins have a problem. WHere can the hydrophobic amino acids hide? What to do wHen there are no globular blobs to keep the water out and feel safe in. But wait - I hear them whisper:
- look at the air!
-wHere?
-over there!
-knocked down, now floating upwards.
-Catch it,
-Wrap it,
-Dip your water-fearing toes in it.
-Ah, blissfull, bubbly relief.
-Everyone happy.
In our confused polypeptide chain wHere some adore and others abHore the watery wetness, air bubbles are the prefect sanctuary. Each fussy amino acid can choose which side of the meniscus to hang out in. Water or Air.
("would you like hydrogen with your oxygen madam?")
And in the process, our long, thin, stretched-out proteins encapsulate the bubble, holding it in place.
Well there you go.
Foam made.
Story end.
Please explain.
Well. to help make our foam, we need to help the temporary denaturing of globular proteins so starting that denaturing process with a little heat or acid works a treat. Sugar increases the viscosity, increasing the shearing force, helping to strech the proteins out.
Copper is the weird one.As you wHisk the eggs a few copper ions dissolve into the mixture and bind to some of the amino acids preventing them from joining back to each other and returning to their orignal gloobular shape and this stabilising the foam. (Silver does the same - for the wealthier chefs amongst you!)
WHat about the Yolk?
This contains fat. A Waterless, lipidy liquid . Hydrophobic amino acids hide inside the fat droplets instead of in the air so the albumins don't surround bubbles and make that cool WHIPped egg white that meringues and mouses are made of (not the ones with horns!!!!)
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