Effects of different magnetic fields on the freezing parameters of cherry

Magnetic field assisted freezing is a kind of freezing methods that can improve food quality. The objective of this study is to evaluate the effects of various magnetic field type and intensity on cherry during the freezing process. The permanent magnetic field (PMF) ranging from 0 to 20 mT and the alternating magnetic field (AMF) ranging from 0 to 2 mT were applied on the cherry. The final temperature and cooling rate of the frozen environment were −30 °C and 4 °C/min. The freezing parameters, which included the macro indexes and microstructure, were used to evaluate the freezing quality. The results show that the freezing temperature was significantly higher in the presence of AMF compared with the control group (p < 0.05). However, the permanent magnetic field had little influence on the freezing temperature. The phase change time decreased with PMF, whereas it increased with AMF, which may consume more energy. The application of magnetic field could reduce drip loss to some extent. Ice crystals formed homogeneously in the cells when the magnetic field was applied. Compared with the control group, the average ice crystal area achieved a reduction of 67% and 78% with PMF and AMF, respectively. Taking all the evaluation indexes into consideration, the optimum magnetic field intensity values were 10 mT for PMF and 1.26 mT for AMF in this study.