The primary physicochemical aspects of freezing are the substantial reduction of water activity and the increase of osmotic pressure by freeze-induced concentration. The temperature-dependent ice fraction subsequently affects the changes in thermal properties and specific chemical reaction processes. In frozen food, the ice structure is strongly determined by the moving ice-front through the balance of water mass transfer and heat transfer. By controlling the ice structure, progressive freeze-concentration could be applied to concentrate liquid food with high quality. In some living organisms, freeze-related biosubstances are produced and accumulated for freeze-tolerance. The cell structure also plays an important role in the freeze-tolerance of cells in microorganisms, plants, and animals.
