Changes in the myosin secondary structure and shrimp surimi gel strength induced by dense phase carbon dioxide

- With increased pressure and temperature of DPCD, the α-helix content of myosin was decreased.
- With increased pressure and temperature of DPCD, the β-sheet content of myosin was increased.
- With increased pressure and temperature of DPCD, the shrimp surimi gel strength was increased.
- The α-helix content was negatively correlated with gel strength.
- The β-sheet content was positively correlated with gel strength.

Dense phase carbon dioxide (DPCD) could induce protein conformation changes. Myosin and shrimp surimi from Litopenaeus vannamei were treated with DPCD at 5-25 MPa and 40-60 °C for 20 min. Myosin secondary structure was investigated by circular dichroism and shrimp surimi gel strength was determined using textural analysis to develop correlations between them. DPCD had a greater effect on secondary structure and gel strength than heating. With increasing pressure and temperature, the α-helix content of DPCD-treated myosin decreased, while the β-sheet, β-turn and random coil contents increased, and the shrimp surimi gel strength increased. The α-helix content was negatively correlated with gel strength, while the β-sheet, β-turn and random coil contents were positively correlated with gel strength. Therefore, when DPCD induced myosin to form a gel, the α-helix of myosin was unfolded and gradually converted to a β-sheet. Such transformations led to protein-protein interactions and cross-linking, which formed a three-dimensional network to enhance the gel strength.