The Food Thread

If you're allergic to eggs, you can use egg-free hydrocolloids designed specifically to mimic the texture of an egg foam. These hydrocolloids can be useful in situations when you need large batches of foam: they stay stable for hours at room temperature, there's less risk of microbial growth than with egg whites, and it's a lot easier to scoop a few spoonfuls of powder than it is to crack and separate dozens of eggs.

The image at the beginning of this section is of a foam made with Methycellulose and xanthan gum, and you can get the recipe here.

Versawhip is made from soy protein and can be used to create both hot and cold foams. It's easy to use: use a scaling of 1% and beat with a blender until a foam forms. Add xanthan gum (0.5% scaling) to create a thicker foam. Unfortunately, the problem with Versawhip is that it tastes bitter and metallic, so the foam has to be sweetened to mask those flavors. For that reason, I rarely use the stuff.
Methylcellulose describes a wide variety of hydrocolloids that do different things. I use MethylCel F50, a formulation best known for its ability to form gels at high temperatures. It works just as easily as Versawhip, but it has less of an undesirable aftertaste. Once again, a 1% scaling with 0.5% xanthan works well for a thick cocktail foam.

For vegans, both Versawhip and methycellulose contain no animal products. Another option is agar (or agar agar), a seaweed-based replacement for gelatin. Use agar as you would gelatin, but keep in mind that agar will gel at a higher temperature, so you may need to use less to achieve the same texture as an equivalent gelatin foam. Agar is available online and at many Asian groceries.