In this study, 2 mT low magnetic field (LMF), 0 mT magnetic field (NMF), and conventional freezing (CF) were used to conduct a 28-day freezing experiment on myofibrillar proteins of silver carp muscle. Changes in the structure and functional properties of the proteins were investigated by measuring surface hydrophobicity, sulfhydryl content, solubility, turbidity, thermal stability, Fourier transform infrared (FTIR) spectra, endogenous fluorescence spectra, and ultraviolet (UV) absorption spectra. The results showed that the application of LMF freezing could inhibit protein aggregation, exposure of interior hydrophobic groups, and α-helix unfolding, weaken α-helix to β-sheet transition and maintain good secondary and tertiary structure stability. There was no significant difference in total sulfhydryl content, solubility, or turbidity between the CF and NMF groups. As it provided lower freezing temperatures, CF inhibited the aggregation of proteins and the exposure of interior hydrophobic groups, but simultaneously made the protein structure sparse and unstable. Compared with CF, LMF freezing could better protect and improve protein structure and function. Overall, LMF freezing can inhibit protein denaturation and maintain good protein structure and function. Compared with CF (-30 ℃), LMF freezing (-20 ℃, 2 mT) has the potential for energy saving.

Protein is an important nutrient required by the human body. The change of protein structure during processing will lead to changes in its functional properties, in turn affecting the quality of foods. There are many physical methods available to alter the structure of proteins to expand their application in the food industry. The new electrophysical processing technology has become a hot spot in the field of food processing due to its advantages of high efficiency, low energy consumption, and slight loss of nutrients. Therefore, this paper reviews the effects of electric field technology (ohmic heating and electrostatic field) and electromagnetic field technology (microwave, radio frequency and magnetic field) on the change of protein structure at multiscales (macroscopic, molecular and microscopic levels), in order provide a theoretical basis for the development and utilization of electromagnetic field processed protein products.