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Lecithin, also known as soy lecithin, is a natural emulsifier and stabilizer. It comes from fatty substances found in plant and animal tissues. It is a traditionally used ingredient in various forms, such as egg yolks, which is why eggs are used to create many emulsions.
Soy Lecithin, or lecithin, is commonly used to hold emulsions together. Lecithin is a very common ingredient in packaged foods because it is such a great emulsifier and stabilizer. It's also the main reason egg yolks work so well to stabilize mayonnaise, aiolis, and sauces like Hollandaise. In modernist cooking it is often used to hold vinaigrettes together, create light foams and airs, and add elasticity and moisture tolerance to doughs.
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Lecithin powder, or lecithin liquid, is just a processed version of lecithin. It has been removed from other ingredients, such as eggs or soy, so it is pure and of a set strength. It also allows you to use it without adding the flavor of eggs to your dishes. Most powdered lecithin is created as a by-product of making soy oils.
Lecithin is very easy to use. It can be blended into liquids of any temperature and begins working right away. For emulsions, it is blended into the liquid before the oil is added. It is also often used with other stabilizers and thickeners such as xanthan gum for added effect.
The amount of lecithin you need to use depends a lot on the technique you are using it for.
For airs and froths using soy lecithin it is typically used at a 0.25% to 1.0% ratio by weight. So for every 100 grams of liquid, 0.25 to 1 gram of soy lecithin would be used.
For the stabilization of emulsions, lecithin is added at a weight ratio of 0.3% to 1.0%, depending on how stabilized you want the emulsion to be. To help strengthen the emulsion, xanthan gum can also be added at a 0.1% to 0.4% ratio, which has the often desired effect of slightly thickening it and increasing the mouthfeel. Note: See How to Measure Modernist Ingredients for more information on ratios.
To make a lecithin foam, take a flavorful liquid and whisk or blend in the lecithin. It is typically used at a 0.25% to 1.0% ratio by weight, so for every 100 grams of liquid, 0.25 to 1 gram of soy lecithin would be used. Most liquids can be kept at this stage for several hours.
Just before serving, introduce air to create bubbles through agitation of some kind. Typically this is done using a whisk or immersion blender, but any type of agitator can be used including an aquarium pump, standing blender, stand mixer with a whisk attachment and a whipping siphon.
Remember that the goal isn't to mix or blend the liquid when you are foaming it but to incorporate air. Because of this, using an immersion blender in a wide container where a quarter of the blender is out of the liquid can be ideal.
Depending on the liquid and the agitation used this will usually take 1 to 5 minutes to fully create the bubbles. You will also have liquid left in the bottom of the container, so don't worry about that.
Let the foam rest for a minute or two for the less stable bubbles to collapse. The foam can be plated directly onto a dish, frozen to make a cold preparation, or any number of other uses. The foams will usually last about 30 to 60 minutes, though they are constantly, if slowly, losing volume once they are created.
The percent of lecithin added is usually between 0.25% to 1% of the weight of the liquid, 0.6% is a good starting point if you are unsure how much to use. Using too much lecithin will actually cause the foam to collapse. The exact amount needed will depend on the specific liquid being used and how watery or oily it is, as well as how many particles are still in it.
The other common use for lecithin is to stabilize emulsions. Lecithin powder will bind and slightly thicken the emulsion, helping it to hold longer before breaking and usually adding a subtle creamy texture to it.
Stabilizing an emulsion with lecithin is very easy. Simply blend in an appropriate amount of lecithin into the emulsion and it should start to stabilize right away.
For an emulsion lecithin will usually be added as 0.5% to 1% of the liquid by weight. To help strengthen the emulsion you can also add some xanthan gum at a 0.1% to 0.4% ratio, which has the sometimes desired benefit of slightly thickening it.