Myofibrillar protein characteristics of fast or slow frozen pork during subsequent storage at −3 °C

This study aimed to investigate the effect of storage at −3 °C on myofibrillar protein in fast or slow frozen pork. Five pork loins at 48 h post-mortem were subjected to either fast (cold metal plate/−80 °C) or slow freezing (still air/−20 °C) followed by storage at −3 °C for 0, 1, 3, and 7 days before thawing. Freezing rate significantly influenced myofibrillar proteins within 3 days at −3 °C, evidenced by higher thaw loss, higher surface hydrophobicity and reduced water-holding of myofibrils, and accelerated appearance of a myosin-4 fragment (160 kDa) in slow freezing. However, these observed differences disappeared after 7 days of storage at −3 °C. The meat pH after thawing did not differ between fast and slow freezing rate. However, the pH values after thawing in both groups decreased with extended storage at −3 °C. Our results suggest that the beneficial effects of fast freezing are gradually lost by holding at −3 °C due to more extensive protein denaturation.