I've made quite a few foams using the standard technique of adding powdered lecithin to my flavor base, and then agitating with an immersion blender in a wide, shallow container, with the blender near the surface so it beats in lots of air. This works ok, but I find the foams don't hold as long as I would like, often just a minute or two. Is there anything I can do to make them more stable for service?
I've found the best foams with lecithin come from two major factors. One is the temp. is should be around 35-45C. the second is to be sure to have some oil or fat content so that the liquid has some thing to emulsify with, which will help stabilize the foam.