In the context of the culinary arena, an emulsion is simply the combining of oil and water, two elements that naturally don’t mix. But to make a good, stable, emulsion, one must first understand its underlying properties.
Classically speaking, most sauces are commonly thickened with some sort of starch, whether it be cornstarch, flower or arrowroot. When these starch granules are added to a sauce, the water element in the sauce makes them swell, adding viscosity.
There is, however, a very different way to thicken a sauce, one that doesn’t require starch. Emulsification.
When making an emulsification, you’re basically cramming little droplets of oil in between water molecules, making it harder for the water molecules to move around. This creates a thick and creamy consistency, which is found in classical sauces such as hollandaise and mayonnaise.
In his book “On Food and Cooking,” Author Harold McGee refers to an emulsion as “Two Liquids: Continuous and Divided.”
The two liquids in an emulsion can be thought of as the container and the contained: one liquid is broken up into separate droplets, and these droplets are contained in and surrounded by the intact mass of the other liquid….The dispersed liquid takes the form of tiny droplets, between a ten-thousandth and a tenth of a millimeter across…The more droplets that are crowded into the continuous phase [read emulsion base], the more they get in the water’s…way, and the more viscous the emulsion is.
To really make an emulsion work, you need shearing power. In culinary school, the first time we made mayonnaise in our basic skills course our instructor forced us to use a metal mixing bowl and a hand whisk. No doubt this masochistic approach was to teach us how easy us modern cooks have it. The problem with using a hand whisk to make an emulsion is that it has very little shearing power.
With modern day equipment on hand, it is much easier for us to make an emulsion just because we have more shearing power at our disposal. A KitchenAid with a whisk attachment, a food processor, and a good blender all have much more shearing power than a hand powered whisk. Why is this important?
Because the more shearing power you have, the smaller your emulsified “droplets” will be, and the less chance you will have of your emulsification separating (breaking). That’s why, when at all possible, I would recommend using a blender to make your emulsions, or at the very least a food processor. But pure shearing power isn’t enough; to really make a good, stable, emulsion, you need emulsifiers.
Emulsifiers are molecules that allow oil and water to play nicely together. These emulsifiers come in two forms. The first is a string type molecule that at one end likes to bond with fat and at the other end likes to bond with water. A typical example of this is lecithin which is found in soy beans and egg yolks.
The second are large protein molecules that will basically block the oil droplets from getting to one another (aka coalesce). Since they are not able to merge, the oil stays suspended in the water, keeping the emulsion from breaking. The protein molecules found in egg yolks and the casein molecules found in cream and milk are the best protein emulsifiers.
One more technique that is used to stabilize emulsions is the use of food grade gums (my favorite being Xanthan).
You can also make a thick puree first and then add your oil or water to that puree. Basically the thickness of the puree will create more pull on the object you are emulsifying, allowing it to disperse more easily and stay suspended in you emulsion base.
For further information on using the emulsion technique, check out these posts.
- How To Make a Stabilized Butter Emulsion Using Xanthan Gum
- Tomato Vierge – The French Man’s Salsa
- A Cheater’s Guide to Green Emulsions
- How To Make Hollandaise – A French Mother Sauce
