Effect of Alternating Magnetic Field-Assisted Freezing Process on the Quality of Frozen Penaeus japonicus

Freezing is a common food preservation method, but conventional freezing often produces large, irregular ice crystals that damage muscle tissue and degrade food quality. This study developed an experimental system using an impact freezer to investigate the effects of alternating magnetic fields (AMF) of different intensities (0 G,20 G,40 G,60 G,80 G) and frequencies (50 Hz,100 Hz,150 Hz,200 Hz,250 Hz) on the freezing behavior and muscle quality of Penaeus japonicus. Results showed that applying a 40 G AMF (AMF-40) significantly reduced freezing time, thawing loss, and cooking loss. It also improved water retention, texture, and color stability. Water distribution analysis indicated that AMF-40 limited the movement and loss of immobilized and free water. Microstructural observations revealed smaller pores and more intact muscle fibers, suggesting the formation of finer ice crystals. Under a 200 Hz AMF (AMF-200 Hz), samples exhibited further decreases in freezing time, thawing loss, and cooking loss, along with significant improvements in hardness, cohesiveness, and resilience, while maintaining muscle color. Enhanced water-holding capacity was also observed, preserving bound water content. Overall, both AMF-40 and AMF-200 Hz promoted the formation of smaller ice crystals and effectively preserved the muscle quality of Penaeus japonicus during freezing, improving the preservation outcome.