Electromagnetic freezing in a widespread frequency range of alternating magnetic fields

The effectiveness of electromagnetic (EM) freezing in improving freezing kinetics and/or the quality of frozen foods constitutes a current controversial topic in Food Technology. The dipolar nature of water could explain potential effects of electric fields on freezing, but the physical basis that supports effects of magnetic fields on freezing is not clear. Therefore, it is in some way striking that the only EM freezers existing at the market are those that generate magnetic, and not electric, fields to assist the freezing process. In this paper, a comprehensive review of the state of the art in EM freezing is presented. The results reported in the literature on the effects of both static and oscillating, either electric or magnetic, fields on supercooling and freezing kinetics are controversial, even for the simplest system, that is, pure water. Moreover, the reviewed results show that frequency and dielectric relaxation could play an important role on water supercooling. Thus, positive effects on freezing have been found in experiments with oscillating, both electric and magnetic, fields of frequencies significantly higher than that of the mains. As oscillating electric fields are induced in the presence of oscillating magnetic fields, this opens a door to explain the potential effects of oscillating magnetic fields on freezing. For a correct interpretation of the data, future research should consider any induced field during the freezing experiments and its potential consequences. All the above reveals the urgent need to perform high-quality scientific research and well-designed experiments, at wide field strengths and frequencies, that can be replicated and confirmed by different laboratories.This work has been supported by the Spanish MINECO through the Project AGL2012-39756-C02-01. A.C. Rodríguez is supported by the BES-2013-065942 pre-doctoral grant, also from MINECO.Peer reviewe