By Harold McGee
Tofu is one of the few foods that can be usefully altered by freezing. When it freezes, the coagulated proteins become even more concentrated, and the solid ice crystals form pockets in the protein network. When the frozen curd thaws, the liquid water flows from the toughened spongy network, especially when the curd is pressed. The sponge is then ready to absorb flavorful cooking liquids, and has a chewier, meatier texture.
From the book On Food and Cooking (2nd edition) by Harold McGee. © 2004 Harold McGee. By permission of Scribner, a division of Simon & Schuster, Inc.