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What causes clumping of fine powder in a liquid? Answered

I make omelettes fairly often.  If the egg yolks are a little on the pale side, I'll add a bit of turmeric - a bright yellow finely powdered spice. Not enough to taste, but enough to add a bit of colour.

I've noticed that if I add the turmeric before I beat the eggs (so it drops on the egg-white), the powder will clump together and stay as blobs.   If I beat the eggs first (with the yolk mixed in) it will spread over the surface and be much easier to combine.

If I use paprika, it will clump whether it's added before or after I've beaten the eggs.

I'm guessing this something to do with electric charge on the surface of the particles, but can someone enlighten me further.

4 Replies

jtobakoBest Answer (author)2011-01-23

How detailed do you want? The powder of the turmeric has small enough particles that the surface tension of the egg white ( or water) can't penetrate the spaces between the particles, so the surface tension creates a bubble around it. When the oils in the yoke are mixed into the white (creating an emulsion) the oils in the spice are able to combine with the egg oils and the mass of particles gets broken up as the liquid flows between them. Paprika is a pepper (fruit), so it doesn't have any oils (just waxes) that are compatible with the egg.

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AndyGadget (author)jtobako2011-01-23

Great answer - Thanks.
Googling around a bit, I see that 99% of the fat content of an egg is in the yolk.

I suspect this is more than just an idle bit on knowledge on you part JT.  Are you in this sort of business?

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jtobako (author)2011-01-24

It's idle bits of knowledge...

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