The antifreeze ability of glutathione was evaluated on the basis of its thermodynamic characteristics and protection of baker's yeast during cryopreservation at -30 degrees C. The thermodynamic characteristics and protection of baker's yeast of glutathione were similar to those of known antifreeze proteins, such as carrot antifreeze protein and holly antifreeze protein. These properties included lowering the freezing point at about 0.20 degrees C non-colligatively, decreasing freezable water content, controlling the movement of free water for its strong hydrophilicity, and improving baker's yeast survival during the simulated processing of frozen dough. Therefore, glutathione was viewed to be an antifreeze protein like substance on the basis of its unique thermodynamic characteristics and protection of baker's yeast. The method combining thermodynamic characteristic analysis and protection evaluation is a new and simple way to screen new antifreeze proteins.