Oil and Water

Forgive me for getting a little off-track with my food additives week, but whenever my white whale Michael Pollan surfaces, the Captain Ahab in me comes out. He breaches! Drop the sails! Lower the boats!

Now that that’s over, let’s talk about emulsifiers, shall we? But before we can do that, we need to back up a bit and talk a little bit about emulsions. Emulsions are, quite simply, mixtures of water and fat (oil). Well, I guess “mixtures” isn’t quite the right word, dispersions is more apt. For as well all know, oil and water don’t mix. Pour some vegetable oil into a quantity of water and each liquid will form its own completely separate layer. Apply a whisk and some elbow grease, however, and it’s possible to break that oil up into lots of tiny droplets. Billions of them, in fact.

That’s an emulsion. Or at least it is temporarily, since before long the forces of surface tension — a liquid’s inclination to minimize its surface area — causes the tiny oil droplets to join together into larger and larger masses until eventually the oil and water are completely separate again. This gets to the heart of the problem with emulsions. Desirable as they are for enriching and thickening various types of liquids, they’re inherently unstable. We therefore need some sort of chemical fixer if we’re going to make them last for any length of time. Enter the emulsifier.

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