High-pressure thawing of pork: Water holding capacity, protein denaturation and ultrastructure

The effects of high-pressure thawing at 70 MPa (35 min), 140 MPa (29 min), and 210 MPa (25 min) were studied for their affect on the water holding capacity, protein denaturation and ultrastructure of porcine longissimus dorsi muscle that was frozen for 24 h at -18 degrees C. For comparison, water thawing at 20 degrees C and air thawing at 4 degrees C were used as control groups. The results showed that thawing losses at 140 MPa were significantly lower (P < 0.05) than those for atmospheric water thawing and the other two high-pressure conditions. However, pressing losses at 70 and 210 MPa were higher. The cooking losses and the degree of protein denaturation increased as the pressure increased. At 210 MPa, the endothermic transition temperature was higher, and the enthalpy of myosin protein denaturation was lower (P < 0.05) than the other treatment groups. At this pressure, the actin peak disappeared. Shrinkage of the sarcomere was observed in the high-pressure thawing groups, and the greatest sarcomere shrinkage was observed at 210 MPa. The H band began to appear blurry at 70 MPa and almost disappeared at 140 and 210 MPa. At the same time, the Z lines became coarser and the I band became considerably wider and white at 210 MPa.