Effects of frequencies ranging from 100 to 400 Hz on electromagnetic field assisted freezing of grass carp (Ctenopharyngodon idellus)

This study aimed to understand the effects of electromagnetic field (EMF) frequencies on the freezing of grass carp tissue. Frequencies ranging from 100 to 400 Hz with a fixed strength of 12 mT were applied during freezing. Results showed that the initial freezing point was significantly increased (p < 0.05) for treatment between 200 and 400 Hz compared with control, but the phase change duration was not affected. Reductions in ice areas and crystal sizes were also observed. The highest initial freezing point of −1.44 °C was obtained at 300 Hz with a 45% reduction in crystal size (19.29 μm). There were also no subsequent changes in the drip, texture, colour and pH values. These results indicated that the oscillation among ions due to applying EMF favoured ice crystallization, and frequencies between 200 and 400 Hz were suitable for improving the freezing process assisted by the electromagnetic field.