My wife loves tequila, especially straight or in a margarita. I wanted to do a fun twist for her so I decided to make a cocktail with tequila that would resemble a beer.
For the foam I wanted to use a citrus air to get some of the flavors of a margarita into it. The citrus air is very flavorful and dissolves on the tongue as you start to drink, almost like sucking on the lime after taking a shot.
All in all it worked out very well!
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 this recipe I wanted to make something that resembled the head on a beer and I decided to use a soy lecithin foam.
The liquid 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 air 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.
For more examples of soy lecithin foams and modernist drinks you can read the excellent Alinea cookbook
or the comprehensive Modernist Cuisine
set.
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.
or the comprehensive 
set.
