Aquafaba is popular because it can provide leavening and structure even though only 1% of it is made of protein. This is likely because aquafaba has saponins. The famous food scientist Harold McGee hypothesizes that the dissolved starch and saponins in bean broth slow the collapse of foam and stabilize bubbles. However, since aquafaba has only 1% protein, its denaturing properties are often inadequate to replace an egg for binding purposes. The addition of a starch solves that problem.