Influence of freeze-thawed cycles on pork quality.

Objective This study was conducted to determine the effect of freeze-thawed cycles (Fresh meat, F-T 1 cycle and F-T 2 cycles) on the quality characteristics of porcine longissimus dorsi muscle. Methods A total of 20 three-crossbred pigs [Duroc × (Large White × Landrace)] were randomly obtained from a commercial slaughterhouse in Thailand. Muscle samples were immediately taken from 10-11th of the longissimus dorsi for histochemical analysis. The muscles were cut into 2.54 cm-thick chops. A minimum of 20 chops were used for each treatment (fresh meat, freeze-thawed 1 and 2 cycles). Individually chops were packaged in polyethylene bags and frozen at -20 °C for 6 months followed by thawing in refrigerator at 4 °C for 24 h (the 1st freeze-thawed cycle). The freeze-thawed procedure was repeated for two cycles (the 2nd freeze-thawed cycle). Thawing loss, shear force value, citrate synthase activity and muscle fiber characteristics were determined on the muscles. Results Results showed that increasing of freeze-thawed cycle increased the thawing loss (P < 0.01) and citrate synthase activity (P < 0.001). Shear force value of fresh meat was higher than freeze-thawed 1 and 2 cycles (F-T 1 cycle and F-T 2 cycles). Freeze-thawed cycles affected muscle characteristics. Muscle fiber area and muscle fiber diameter decreased with an increasing number of freeze-thawed cycles (P < 0.001), while the thickness of endomysium and perimysium were increased (P < 0.001). Conclusion Repeated freeze-thawed cycles degraded muscle fiber structure and deteriorated pork quality.