Anyone who has pressed a block of tofu can tell it’s a fairly waterlogged product. According to America’s Test Kitchen, tofu is 86 percent water. When frozen, all of the water within the tofu turns to ice and expands, pushing against the cell walls of the soy proteins and creating larger holes and caverns within the block.
Thawing melts the ice and the water seeps out, but the holes remain. This makes for a more porous, spongier, and firmer tofu that’s primed to soak up a sauce and be fried, baked, or marinated. It’s tofu at its best.
Via https://vegnews.com/freezing-tofu-recipe-game-changer