Making panna cotta has reminded me once again what a truly remarkable substance gelatin is. It has the ability to turn virtually any liquid into a wiggly, trembling semi-solid. Something for which my 2-year-old daughter will be forever grateful. How can a mere protein powder be responsible for feats as spectacular as these? Because of its highly unusual chemical composition.
Virtually every protein molecule in the natural world responds to heat in the same way: first, by unfolding from a tight clump into a long languid strand. Second, by bonding permanently to other nearby protein molecules to form a tight, solid mass (think scrambled eggs and you’ve got the idea). Gelatin molecules do the unfolding and bonding thing, but with one very important difference: the bonds they form with other gelatin molecules are extremely weak, apply a little heat to them and they break. Should those gelatin molecules happen to be immersed in a liquid like fruit juice at the time their bonds are broken, they’ll disperse through that liquid, and as they cool, try to re-bond to one another. Only now there are some water molecules in the way, which keep the gelatin molecules from forming a tight mesh. At the same time, the water molecules are caught, locked in place by those gelatin molecules that do manage to get hold of one another. The result is not quite a solid, not quite a liquid. It’s Jell-O.