Effects of Electric and Magnetic Field on Freezing and Possible Relevance in Freeze Drying

Application of an electric or magnetic field can significantly affect the freezing characteristics of water. A DC electric field will tend to induce ice nucleation at a lower degree of supercooling, and there is evidence to show that an AC electric field delays the onset of ice nucleation. Industrial research has shown that a magnetic field can be used to delay nucleation and to induce small, unclustered ice. Smaller ice crystals are essential in the preservation of the structure or bioavailability of frozen materials, particularly biological or food products. On the other hand, larger ice crystals facilitate faster freeze drying because it results in less vapor mass transfer resistance. The end part of this review introduces another application of magnetic field in the form of magnetocaloric freezers. This technology is a potential alternative to heat pump drying for commercial freezing and refrigeration.