Effects of Magnetic Fields on Freezing: Application to Biological Products

Abstract

Magnetic freezing is nowadays established as a commercial reality mainly oriented towards the food market. According to advertisements, magnetic freezing is able to generate tiny ice crystals throughout the frozen product, prevent cell destruction, and preserve the quality of fresh food intact after thawing. If all these advantages were true, magnetic freezing would represent a significant advance in freezing technology, not only for food preservation, but also for cryopreservation of biological specimens such as cells, tissues, and organs. Magnetic fields (MFs) are supposed to act directly on water by orientating, vibrating, and/or spinning molecules to prevent them from clustering and, thus, to promote supercooling. However, many doubts exist about the real effects of MFs on freezing and the science behind the potential mechanisms involved. To provide a basis for extending the understanding of magnetic freezing, this paper presents a critical review of the materials published in the literature up to now, including both patents and experimental results. After examining the information available, it was not possible to discern whether MFs have an appreciable effect on supercooling, freezing kinetics, ice crystals, quality, and/or viability of the frozen products. Experiments described in the literature frequently fail to identify and/or control all the factors that can play a role in magnetic freezing. Moreover, many of the comparisons between magnetic and conventional freezing are not correctly designed to draw valid conclusions, and wide ranges of MF intensities and frequencies are unexplored. Therefore, more rigorous experimentation and further evidence are needed to confirm or reject the efficacy of MFs in improving the quality of frozen products.

Thermal conductivity of ice prepared under different conditions

“…These processes were studied to determine suitable strategies for controlling ice nucleation. [10] One of the most common RFPs is the individual quick frozen (IQF) procedure. It is well known that the freezing rate plays an important role in food quality.…”

External Field Assisted Freeze Casting

“…The second term on the right-hand side is due to the curvature effect, while the third term is due to premelting effects. External fields can also alter the freezing point of water because it is a strongly polar, weakly diamagnetic molecule [135]. In its liquid state, H 2 O molecules form loose networks of ring-like structures of various shape and size [135].…”

“…External fields can also alter the freezing point of water because it is a strongly polar, weakly diamagnetic molecule [135]. In its liquid state, H 2 O molecules form loose networks of ring-like structures of various shape and size [135]. To freeze, the water molecules must rearrange to initiate the nucleation of ice crystals [136].…”

Methods for (industrial) thawing of fish blocks: A review

“…A further study has investigated optimal parameters for HVEF, in particular the spacing between electrode and cathode and the applied voltage (Bai, Sun, Li, & Kang, 2011). Mertens and Knorr (1992) describe oscillating magnetic field pulses for nonthermal food preservation, whereas Otero, Rodríguez, P erez-Mateos, and Sanz (2016) conclude that at least for freezing, the benefits of using magnetic fields is not proven and that more research has to be conducted. There is a lack of data concerning this thawing method with respect to fish and fishery products, and hence more research is needed in this direction.…”