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One of the most popular methods in molecular gastronomy is the creation of foams. While they are associated with modernist cuisine, foams have been used for centuries and range from meringues and whip cream to bread and quiche.
With some of the new molecular gastronomy ingredients such as soy lecithin you can now make culinary foams that are exceptionally light. There are several ways to make a soy lecithin foam including using iSi canisters. However, we will go low tech in this article and show you how to make soy lecithin foam with an immersion blender.
A foam is basically air whipped into a liquid until bubbles are created. If these bubbles are stabilized then it is considered a stable foam. There are three components to making a stable foam: a stabilizer, the liquid, and air.
The role of the stabilizer is to help maintain the structure of the foam. This can be done in many different ways, from baking, where the foam is stabilized as the flour cooks, to meringues, where the foam is stabilized by the egg whites. In soy lecithin foams the stabilizer is always soy lecithin. It allows the foam to last longer without greatly changing the nature of it.
Soy lecithin is typically added by weight as 0.3% to 1% of the total weight of the liquid. The amount used will depend on the specific ingredient you are trying to foam, which is why it varies so much. However, lecithin foams do not require nearly as much precision as some other modernist techniques.
In soy lecithin foams the liquid can be almost any water-based liquid since lecithin works well with both acid and base ingredients. The liquid should be very strong since it will be diluted once the air is incorporated into it. Some typical liquids are citrus juices, soy sauce, teas, and other flavorful liquids.
Typically, "normal" air is used with the foams but if you use an iSi canister then the air will be nitrous oxide or whatever else you use to charge it. Unless you use an iSi canister you will usually incorporate the air into the liquid using a whisk, immersion blender, or other mixing device.
The first thing to do when making a soy lecithin foam is to dissolve the lecithin in the liquid using a whisk or hand blender. This can be done with the liquid at room temperature, or a slightly warmer temperature similar to the temperature of hot tap water. Once it is mixed it can stay in this state for several hours before being foamed.
The second thing to do is to make the actual foam. This involves whipping the liquid until it forms a foam, typically with a whisk or immersion blender but various kitchen appliances will work fine as long as they incorporate air into the container. Once the liquid has foamed you let the foam rest for a minute to stabilize, then you can spoon it out and use it. Depending on the liquid it should last anywhere from 30 minutes up to a few hours, but the sooner you use it the better.
Pour the liquid and soy lecithin mixture into a wide, flat bottomed container. This helps keep the liquid shallow so when you use the immersion blender it will be mixing air into the liquid much more than if the whole blender was submerged.Using the immersion blender, blend the liquid until it creates a large amount of foam. This process can take anywhere from 60 seconds up to a few minutes. Let the foam stabilize for a minute and then you can use it.