For a cheese puff recipe it seems to be missing a couple of things. A leavener for starters. There’s no yeast and no baking powder. And then there’s the flour thing…there isn’t any. No wheat flour at any rate. Instead we have manioc flour, also known as the dried and ground starch of the cassava (also known as yuca) root. It’s the same starch that tapioca is made from, in case that helps.
So how do these things work? The secret is the extraordinary viscosity of cassava starch. When the granules are heated and moistened they gelatinize almost instantly, then stick together like glue. As the air bubbles inside the batter heat and begin to fill with steam, the gluey network that surrounds them maintains its integrity, stretching to accommodate the increase in volume — and the bun rises.
It’s a marvelous property, but it only lasts for so long. For “gelatinize” is another word for “dissolve”…at least where starch granules are concerned. Partial gelatinization means you have little bundles of starches that are only just coming apart…such that the long, reed-like molecules that make them up are getting tangled up with one another. Full gelatinization means that the bundles have come completely apart, which isn’t a good thing where starches are concerned. For unlike proteins (which make “real” gels), starch molecules don’t bond to each other. Which means that without larger masses in the mix to help anchor them they eventually start to flow like so many pieces of straw in a river. And the dough starts to liquify.
So one of the tricks to good pão de queijo is to be quick about your mixing, shaping and baking.