Effect of pulsed electric field pre-treatment combined with static magnetic field freezing on strawberry quality

This study investigated the synergistic effects of pulsed electric field pre-treatment combined with static magnetic field freezing (EMF) on strawberry quality. Compared to conventional freezing (CF), EMF significantly reduced phase transition time by 27.65 % and total freezing time by 21.8 % while increasing the average freezing rate by 26.9 %. EMF increased hardness by 19.3 %, reduced drip loss by 32.0 %, and best preserved the color by yielding the highest a* value and the lowest total color difference (∆E) compared to fresh samples. In addition, EMF increased the total anthocyanin and ascorbic acid content by 14.8 % and 10.2 %, respectively, improving the antioxidant capacity. Water distribution analysis revealed that EMF minimized free water conversion and maintained tissue moisture homogeneity. Microstructurally, EMF reduced the ice crystal area by 26.5 %, mitigating cell damage and maintaining structural integrity, as confirmed by the reduction in malondialdehyde content and relative conductivity. This integrated approach offers a promising strategy for high-quality fruit freezing.

Industrial relevance

Combined electric-magnetic field technology addresses key limitations of conventional fruit freezing, including slow freezing speeds, large ice crystal formation and severe quality loss. By increasing freezing efficiency and improving product quality (texture, color, nutrient retention), this approach reduces post-thaw losses and increases market value. Its non-thermal nature aligns with clean-labelling trends and offers energy-saving potential for industrial scale. The technology provides a theoretical basis for developing high-quality frozen strawberry products with similar freshness characteristics, supporting the expansion of the seasonal fruit supply chain.