Within molecular gastronomy one of the easiest things to experiment with are foams. There are a lot of ingredients that can cause foams, and a lot of variety depending on what type of foam you are trying to make. For my preparation I wanted to make an "air", basically a really, really light foam, similar to the fizzy head you get when you pour soda or a light beer. For this type of foam soy lecithin is perfect.
For this soy lecithin citrus air recipe I wanted to make something that resembled the head on a beer and I decided to use a soy lecithin foam.
The liquid to foam I settled on was a combination of lime and lemon juice. The recipe was inspired from the lemon air from Albert y Ferran Adrià.
However, I planned to use the soy lecithin citrus foam on tequila so I wanted to make sure most of the flavor was lime and I didn't water it down as much since the flavor would have to stand up to straight tequila.
You can see the instruction for the final dish here: Frothy Tequila with Citrus Air Recipe.
In general, to make a soy lecithin "air" you want to combine about 0.4% to 0.6% soy lecithin, by weight, with a liquid. Then using a hand blender to incorporate air into the mixture. The air will last for 15 to 30 minutes and can also be frozen for weeks.
If you like this recipe you can get more than 80 other recipes from my book Modernist Cooking Made Easy: Getting Started. The book covers many of the popular modernist techniques such as gelling, spherification, and foams. It also explores modernist ingredients like agar, sodium alginate, tapioca maltodextrin, and xanthan gum. It is all presented in an easy to understand format and I think it's the best way to learn about modernist cooking.
Also, if you are just getting started experimenting with molecular gastronomy and modernist cuisine then I highly recommend one of these molecular gastronomy kits. They have everything you need to do many different dishes.
Combine all of the ingredients in a wide, flat bottomed container.When ready to serve, blend the soy lecithin citrus mixture using an immersion blender until a nice head of foam develops. Let the soy lecithin citrus air sit for 1 minute to stabilize and then spoon it out onto your dish.