Influence of pulsed electric field on thawing of frozen pork: Physical properties, fat oxidation and protein structure

This study explored the effects of constant-voltage pulsed electric field thawing (CV-T) and constant-current pulsed electric field thawing (CC-T) on electrical characteristics, temperature distribution and qualities of porcine longissimus dorsi muscle, considering air thawing (AT) and water immersion thawing (WT) for the comparison, additionally making fresh meat (FM) as the control. The results demonstrated that the impedance of pork decreased rapidly from -20 to -8 °C, while the changing trend slowed down from -8 to 0 °C; higher frequency was conducive to lowering its impedance and to the thawing. In terms of the effect, pulsed electric field thawing reduced the duration by 33% to 85%, avoiding the loss significantly (P<0.05); however, there was no significant difference in cooking loss (P>0.05). CC-T indicated better temperature uniformity than CV-T, and consistently maintained the surface temperature difference at 0.3 - 9 °C. Therefore, CC-T significantly reduced water migration, muscle damage as well as protein and fat oxidation during the process (P<0.05), meanwhile maintaining colour, water retention and texture properties of the muscle. Circular dichroism and fluorescence spectrometry indicated that CC-T significantly reduced cross-linking, aggregation and sedimentation of myofibrillar proteins (P<0.05) with more stable secondary and tertiary structures than other treatments. In addition, microstructural observations showed that CC-T reduced muscle damage owing to ice crystal rapid melting. Therefore, CC-T could improve the thawing speed, temperature rise uniformity, and quality of pork, which demonstrates the potential of the CC-T method for application.