gelatin, the transparent protein extract (collagen) that is crucial for holding liquids in suspension, gives shimmering architectural jellies, Bavarian creams, and similar preparations their drama. Water molecules bond with gelatin molecules to produce an elastic solid (colloidal sol). About 7 grams (1 tablespoon) of gelatin will bind a pint of liquid. Powdered, granular, or sheets of commercial gelatin first need to be hydrated in liquid three to four times their volume; they are then activated by heating (usually the soaking bath), or by adding a sheet to the hot liquid preparation. In the refrigerator, the gelatin solidifies by cooling slowly to a lower temperature. The gelatin network continues to tighten its water-holding capacity, but after aging over a few days, the bonds begin to break and liquid escapes (syneresis).
